4 CHAPTER 2 S SH 3 4 3 6 6 7 5 Metal Complexes of...

38

CHAPTER – 2

Metal Complexes of Pyrimidine - 2 - thione and Purine - 6 - thione

This chapter describes a series of complexes of palladium(II), platinum(II),

ruthenium(II) and copper(I) metal ions with pyrimidine - 2 - thione (pymSH, I) and

purine - 6 - thione (puSH2, II) with mono- and di- tertiary phosphines as co-ligands as

shown in Chart 2.1. These thio-ligands exist as thione – thiol tautomers (Ia, Ib; IIa, IIb).

The uninegative pyrimidine - 2 - thiolate and dinegative purine - 6 - thiolate can be

representated as resonating structures as (IIIa and IIIb) and (IVa and IVb) respectively.

Triphenylphosphine, (C6H5)3P

1,1-bis(diphenylphosphino)methane, Ph2P-(CH2)-PPh2, dppm

1,2-bis(diphenylphosphino)ethane, Ph2P-(CH2)2 -PPh2, dppe

1,3-bis(diphenylphosphino)propane, Ph2P-(CH2)3 -PPh2, dppp

1,4-bis(diphenylphosphino)butane, Ph2P-(CH2)4 -PPh2, dppb

Chart - 2.1

In literature, complexes of pyrimidine – 2 - thione and purine - 6 - thione with

Ru(II), Pd(II) and Pt(II) have been reported, but mostly the co-ligand is trimethyl

phosphine or carbonyl group [84-91, 115-127]. Only a few complexes of these metals are

N

N S

Ia

HN

N

N

N

S

IIa

67

8

91

12

2

3

3

4

4

55

6

HH

N

N S-

N

N S_

IIIa IIIb

N

N

N

N

S-

-

N

N

N

N

S-2

IVa IVb

N

N SH1

2

34

5

6

Ib

N

N

N

N

SH6 7

8

9

1

2

34

5

H

IIb

39

reported with monotertiary phosphines as co-ligands, namely, [Ru(PPh3)2(η2-N, S-

pymS)2]Cl2∙2H3O+ 51 [85], [Ru(PPh3)2(η

2-N, S-puSH2)2](ClO4)2 56 [91], [Pd(η

2-N, S-

pymS)(PPh3)2](ClO4) 76 [118], and [Pd2(η2-N, S- pymS)2(PMe3)2Cl2] 77 [119], and none

with di-tertiary phosphines. As regards copper(I), complexes of neutral pyrimidine - 2 -

thione, with tertiary phosphines as co-ligands, are known in literature [131-135, 139-

140], but not a single complex with purine-6-thione with tertiary phosphine as co-ligand

is reported. Pyrimidine – 2 - thione is either neutral or anionic in these complexes.

In the present investigation, complexes of Ru(II), Pd(II), Pt(II) and Cu(I) with

pyrimidine - 2 - thione and purine - 6 - thione have been studied using a series of mono-

and di- tertiary phosphines as co-ligands (Chart 2.1). Table 2.1 gives a list of complexes

synthesized. These complexes are characterized by CHN analysis, Infrared spectroscopy,

1H,

13C and

31P NMR spectroscopy and X- ray crystallography.

Table 2.1. List of Complexes Synthesized

Complex Structure of

ligand

Characterized by

[Pd(η2-N

1,S- pymS)(η

1-S- pymS)(PPh3)] 1

N

N S-1

CHN, x-ray, IR and

NMR spectroscopy

[Pd(η1-S-pymS)2(dppm)] 2

N

N S-

CHN, IR and NMR

spectroscopy

[Pd(η1-S- pymS)2(dppe)] 3

N

N S-

CHN, x-ray, IR and

NMR spectroscopy

[Pd(η1-S- pymS)2(dppp)] 4

N

N S-

CHN, IR and NMR

spectroscopy

[Pd(η1-S- pymS)2(dppb)] 5

N

N S-

CHN, IR and NMR

spectroscopy

[Pd(η2-N

7,S- puS)(PPh3)2] 6

N

N

N

N

S-

-

CHN, IR and NMR

spectroscopy

40

[Pd(η2-N

7,S- puS)(dppm)] 7

N

N

N

N

S-

-

CHN, IR and NMR

spectroscopy

[Pd(η2- N

7,S- puS)(dppp)] 8

N

N

N

N

S-

-

CHN, x-ray, IR and

NMR spectroscopy

[Pd(η2-N

7,S- puS)(dppb)] 9

N

N

N

N

S-

-

CHN, IR and NMR

spectroscopy

[Pt(η2-N,S- pymS)(η

1-S- pymS)(PPh3)] 10

N

N S-1

CHN, x-ray, IR and

NMR spectroscopy

[Pt(η1-S- pymS)2(dppm)] 11

N

N S-

CHN, x-ray, IR and

NMR spectroscopy

[Pt(η1-S- pymS)2(dppe)] 12

N

N S-

CHN, IR and NMR

spectroscopy

[Pt(η1-S- pymS)2(dppp)] 13

N

N S-

CHN, IR and NMR

spectroscopy

[Pt(η1-S- pymS)2(dppb)] 14

N

N S-

CHN, IR and NMR

spectroscopy

[Pt(η2-N

7,S- puS)(PPh3)2] 15

N

N

N

N

S-

-

CHN, IR and NMR

spectroscopy

[Pt(η2-N

7,S- puS)(dppm)] 16

N

N

N

N

S-

-

CHN, IR and NMR

spectroscopy

[Pt(η2-N

7,S- puS)(dppp)] 17

N

N

N

N

S-

-

CHN, IR and NMR

spectroscopy

41

[Pt(η2-N

7,S- puS)(dppb)] 18

N

N

N

N

S-

-

CHN, x-ray, IR and

NMR spectroscopy

[Ru(η2-N

1,S- pymS)2(PPh3)2] 19

N

N S-1

CHN, x-ray, IR and

NMR spectroscopy

[Ru(η2-N

1,S- pymS)2(dppm)] 20

N

N S-1

CHN, IR and NMR

spectroscopy

[Ru(η2-N

1,S- pymS)2(dppe)] 21

N

N S-1

CHN, IR and NMR

spectroscopy

[Ru(η2-N

1,S- pymS)2(dppp)] 22

N

N S-1

CHN, x-ray, IR and

NMR spectroscopy

[Ru(η2-N

1,S- pymS)2(dppb)] 23

N

N S-1

CHN, IR and NMR

spectroscopy

[CuCl(η1-S-pymSH)(PPh3)2] 24

N

N S-1

CHN, x-ray, IR and

NMR spectroscopy

[CuBr(η1-S-pymSH)(PPh3)2] 25

N

N S-1

CHN, x-ray, IR and

NMR spectroscopy

[Cu2(μ-I)2(PPh3)2(μ-N3,S-pymSH)]∙CH3CN 26

N

N S-1

3

CHN, x-ray, IR and

NMR spectroscopy

[Cu(η2-N

7,S-puSH)(PPh3)2]∙CH3OH 27

CuCl + puSH2 + 2PPh3 N

N

N

NH

S-

CHN, x-ray, IR and

NMR spectroscopy

[Cu(η2-N


CuBr + puSH2 + 2PPh3

* 27 and 28 differ in their packing arrangements

and some other parameters.

N

N

N

NH

S-

CHN, x-ray, IR and

NMR spectroscopy

42

[CuI(η1-S-puSH2)(PPh3)2] 29

HN

N

N

NH

S

CHN, x-ray, IR and

NMR spectroscopy

[Cu6(2-I)(3-I)4(4-I)(m-tolyl3P)4(CH3CN)2] 30*

* CuI reacted with pymSH and m-tol3P, in

acetonitrile and chloroform, gave cluster 30.

pymSH did not bind with it.

N

NH

S

CHN, x-ray, IR

spectroscopy

Palladium(II) Complexes

Synthesis

Reaction of [PdCl2(PPh3)2] [194] with pyrimidine -2-thione (pymSH) in 1 : 2

molar ratio in the presence of NaOH in ethanol formed a yellow colored solution, which

on slow evaporation yielded crystals of stoichiometry, [Pd(η2-N

1,S-pymS)(η

1-S-

pymS)(PPh3)] 1. In this preparation, aqueous sodium hydroxide was used as a base

which removed the chloride anion as NaCl salt. Similar reaction of [PdCl2(dppm)] with

pyrimidine -2-thione (pymSH) in 1 : 2 molar ratio in the presence of NaOH in ethanol

gave yellow orange complex of stoichiometry, [Pd(η1-S- pymS)2(dppm)] 2. Complexes

[Pd(η1-S-pymS)2(dppe)] 3, [Pd(η

1-S-pymS)2(dppp)] 4 and [Pd(η

1-S-pymS)2(dppb] 5 were

prepared using [PdCl2(dppe)], [PdCl2(dppp)] and [PdCl2(dppb)] as the starting materials

by following the above procedure.

PdCl2(PPh3)2 +N

N S

H

[Pd(2-N1,S-pymS)(1-S- pymS)(PPh3)]

1

2NaOH

-NaCl

PdCl2(dppm) + [Pd(1-S- pymS)2(dppm)]

2

pymS- = N

N S-

N

N S

H

1

3

2NaOH

-NaCl

43

These complexes are soluble in dichloromethane, chloroform, acetone and other

organic solvents. Scheme 2.1 gives a bonding view of complexes. The x-ray structures of

1 and 3 have shown that these complexes have square planar geometries. In complex 1,

one deprotonated pymS- is coordinating via

1 - N, S- donor atoms in a chelation mode

and the other one is pendant coordinating via 1

- S donor atom. This mixed coordination

mode of pymS- in complex 1 is first one of its kind reported in metal - pyrimidine-2-

thione chemistry [1-4]. In complexes 2 – 5, the deprotonated pymS- ligands are

coordinating via 1

- S donor atoms. In literature, there are only two complexes, [Pd(η2-

N1,S-pymS)(PPh3)2](ClO4) 77 [118], and [Pd2(µ-N

1,S- pymS)2(PMe3)2Cl2] 78 [119]

known in which pyrimidine -2-thiolate is chelating in the former and bridging in the

latter complex.

Palladium(II) - purine - 2 - thione complexes have been prepared similarly. In a

typical reaction, [PdCl2(PPh3)2] with purine - 6 - thione (puSH2) in 1 : 2 molar ratio in

ethanol in presence of NaOH gave the yellow crystalline complex of stoichiometry,

[Pd(η2-N

7,S- puS)(PPh3)2] 6, unlike complex 1 with a different stoichiometry. In

complex 6, there is only one purine-6-thiolate, acting as a dianion and is chelating, but in

complex 1, two pyrimidine-2-thiolate units are bonded, one pyrimidine-2-thiolate is

chelating and the other one is S-bonded.

Pd

PPh3S

N NS

Pd

P

P NS

NS

dppm,2dppe, 3dppp, 4dppb, 5.

Scheme 2.1

P P =S N =

1 2 - 5

1-5

N

N S-1

3

44

PdCl2(PPh3)2 +N

N

N

N

SH

H

[Pd(2-N7,S- puS)(PPh3)2]

6

puS2- = N

N

N

N

S-2

2NaOH

-NaCl

7

7

Reactions of [PdCl2(dppm)], [PdCl2(dppp)] and [PdCl2(dppb)] with purine-6-thione in

the presence of NaOH yielded complexes, [Pd(η2-N

7,S- puS)(dppm)] 7, [Pd(η

2-N

7,S-

puS)(dppp)] 8 and [Pd(η2-N

7,S- puS)(dppb)] 9, in which the purine-6-thiolate dianion is

chelating.

Complexes 6 – 9 are soluble in dimethylsulphoxide and are not soluble in

dichloromethane, chloroform and acetone. Scheme 2.2 gives a bonding view of

complexes. The x-ray structure of 8 has shown that these complexes of Pd(II) have

square planar geometry with deprotonated puS2-

coordinating via N7, S- donor atoms in

chelation mode.

Pd

PPh3S

N

Pd

P

P N

S

dppm,7dppp, 8dppb, 9

Scheme 2.2

P P =S N =

PPh36 7 - 9

6-9

N

N

N

N

S-2

45

IR Spectroscopy

The IR spectrum of free pyrimidine - 2 - thione shows a characteristic broad peak

at 3300 cm-1

due to ν(N – H). The absence of this peak in complexes 1 - 5 shows

deprotonation of the thio - ligand. The ν(C – S) peak of free ligand pymSH at 980s cm-1

shows low energy shift to 810 - 885 cm-1

in complexes (Table 2.2). The presence of

characteristic ν(P – C) peaks at 1084-1120 cm-1

reveals the coordinated tertiary

phosphines in complexes. The peaks due to ν(C – N), ν(C – C) and δ(N – H) lie in the

region, 1434 - 1575 cm-1

.

The IR spectrum of free purine - 6 - thione shows an intense peak at 3400 cm-1

due to ν(N – H), which also incorporates ν(O – H) stretching band of the ligand

(hydrated ligand). The absence of this peak in complexes 6 - 9 shows deprotonation of

ligand and it is coordinating as dianion via N7, S donor atoms. The ν(C = S) peaks in all

the complexes show low energy shifts to 836 - 860 cm-1

as compared to that in free

ligand 868 cm-1

. The presence of characteristic ν(P – C) peaks in the region, 1080 - 1125

cm-1

reveals the coordinated tertiary phosphines in complexes. The peaks due to ν(C –

N), ν(C – C) and δ(N – H) lie in the region, 1440 - 1573 cm-1

. The IR data of these

complexes reveal that ν(C = S) peaks shift to low energy region, which indicates sulphur

coordination in all the complexes. Also there are no N-H peaks in the complexes,

probably nitrogen is also coordinating in some complexes.

46

Structures of Pd(II) complexes

The crystal structures of three representative complexes, namely, [Pd(η2-N,S-

pymS)(η1-S- pymS)(PPh3)] 1, [Pd(η

1-S- pymS)2(dppe)] 3 and [Pd(η

2-N, S- puS)(dppp)]

8 were obtained and are described in this section. Complexes 1, 3 and 8 crystallized in

monoclinic crystal systems different space groups (Tables 2.3 - 2.6).

Complex [Pd(η2-N,S-pymS)(η

1-S-pymS)(PPh3)], 1, has two pyrimidine-2-thiolate

(pymS-) and one PPh3 ligands coordinating to Pd center (Figure 2.1). One pymS

- anion is

chelating via N3, S - donor atoms forming a four membered metallocyclic ring with a bite

angle, N(3)-Pd-S(1), of 69.21(8), and second pymS- anion is S-bonded. This bite angle

is similar to that in analogous complexes [118,119]. The trans bond angles, S(I)-Pd-S(2)

{166.02(3)} and N(3)-Pd-P {167.74(8)} reveal that the geometry is severely distorted

from a square plane (Table 2.7). When pymidine-2-thiolate is chelated, the bond angle,

Pd-S(1)-C(26) 80.60(12), is much shorter than the bond angle, Pd-S(2)-C(19),

103.48(12), when it is S-bonded. Therefore, this Pd – S – C bond angle is indicative of

bonding modes of pyrimidine-2-thiolate. The Pd – S bond distances, 2.345(12) Å and

Table 2.2: The IR data (in cm-1

) of complexes 1 – 9.

Complexes (N H) (C H) (C C) ..., (C N) ...

, (N H) (C S) (P C)

pymSH 3300br 2910w 1560m, 1460s, 1480s 980br -

1 - 3060w 1575s, 1480s 850w,820w 1090m

2 - 3049w 1562s,1481s 885m,850w 1084m

3 - 3049w 1562s, 1485s 879m,819s 1101m

4 - 3049w 1560s, 1436m 840m,820s 1120m

5 - 3049w 1558s, 1434m 841m,810s 1120m

pusH2 3431s 3095w 1573m,1471s 868s -

6 - 3080w 1555w,1440s 860m 1125m

7 - 3080w 1545s, 1450s 860m 1080m

8 - 3047w 1537s,1481m 836s 1101m

9 - 3090w 1550w,1440s 840m 1120m

47

2.321(11) Å are nearly equal. The Pd – N bond distance is 2.093(3) Å. Somewhat

different Pd - S bond distances are due to the nature of bonding by pyrimidine-2-thiolate.

The Pd – S bond distance is longer when pyrimidine-2-thiolate is chelated as compared to

when it is S-bonded. These Pd – S, Pd – N and Pd – P bond distances are comparable to

the literature values, {2.293(1) Ǻ, 2.143(3) Ǻ and 2.236(1) Ǻ in [Pd2(µ -N, S-

pymS)2Cl2(PMe3)2] 77 [119]}.

Figure 2.1. Molecular structure of [Pd(η2-N

3,S- pymS)(η

1-S- pymS)(PPh3)] 1 with

numbering scheme.

The packing diagram of 1 reveals that the sulphur atom of chelated pymS- of one

molecule interacts with C4- H atom of S - bonded pymS

- of second molecule with

CH∙∙∙S interaction of 2.798 Ǻ (C∙∙∙S, 3.619 Å; C-H∙∙∙S angle, 147.92°) (sum of van der

Waals radii of S and H, 3.00 Ǻ [195]) (Figure 2.2). This interaction occurs linearly and it

constitutes one dimensional chain. The one 1D chain interacts with another 1D chain

through CH∙∙∙π interactions {2.746, 2.891 Ǻ} (C∙∙∙C, 3.479, 3.801 Å; C-H∙∙∙C angle,

136.32, 166.39°) forming 2D network.

48

Figure 2.2. Packing diagram of [Pd(η2-N

1,S- pymS)(η

1-S- pymS)(PPh3)] 1.

In complex, [Pd(η1

-S - pymS)2(dppe)], 3, two pyrimidine-2-thiolates (pymS-) and

one dppe ligand are coordinating to Pd center (Figure 2.3). Due to P, P- chelation by

dppe, two pymS- anions adopt η

1-S- bonding mode. Thus bonding patterns of 1 and 3 are

different due to chelation by dppe. The two trans P-Pd-S, bond angles, {172.91(2),

175.04(2)} reveal that the square planar geometry is less distorted than that of 1 (Table

2.7). The bond angles around Pd lie in the range, 84.84(2) - 95.68(2) and show a

distorted square plane. Since pyrimidine-2-thiolate is S-bonded, the Pd-S(1)-C(11) and

Pd-S(2)-C(21) bond angles 97.91(9) and 102.11(9) respectively are similar to

103.48(12) as observed for η1- S - pymS

- bonded ligand in 1. Both Pd – S and Pd – P

bond distances are nearly equal, {Pd – S, 2.3793(7), 2.3822(7) Å; Pd – P, 2.2767(6),

2.2773(7) Å}. These Pd – S and Pd – P bond distances are comparable to the literature

values [47-48, 118-119].

49

Figure 2.3. Molecular structure of [Pd(η1-S- pymS)2(dppe)] 3 with numbering scheme

The packing diagram of 3 shows intra- as well as inter-molecular interactions

(Figure 2.4). The intra-molecular contact, 3.126 Ǻ, is between S and N of pyrimidine-2-

thione within the same molecule (sum of the van der Waals radii of S and N, 3.350 Ǻ

[195]). The inter-molecular contact is between the N atom of one molecule with H atom

of phenyl ring {CHphenyl∙∙∙N, 2.709 Ǻ}(N∙∙∙C, 3.529 Å; N-H∙∙∙C angle, 147.65°). The

same N atom is interacting also with H atom of CH2 (dppe) {CH∙∙∙N, 2.482 Ǻ} (N∙∙∙C,

3.362 Å; N-H∙∙∙C angle, 150.70°) (sum of van der Waals radii of N and H, 2.750 Ǻ

[195]). These weak interactions lead to formation of 1D polymer. Two 1D chains are

interacting through CHpyrimidyl∙∙∙πphenyl, 2.782 and 2.839 Ǻ (C∙∙∙C, 3.531, 3.742 Å; C-

H∙∙∙C angle, 138.43°, 164.09°) and form a sheet structure.

50

Figure 2.4. Packing diagram of [Pd(η1-S- pymS)2(dppe)] 3.

As we change the ligand from pyrimidine - 2 - thione to purine - 6 - thione,

different bonding modes are observed. In complex [Pd(η2-N

7,S- puS) (dppp)] 8, the

ligand is acting as a dianion and both puS-2

and the co-ligand dppp are chelating (Figure

2.5). Despite P, P- chelation by dppp, the thio-ligand is in N7,S - chelation mode and is

unlike the bonding mode of pyrimidine - 2 - thiolate as observed in complex 3. The two

trans, N(1)–Pd(1)–P(2) and S(1)–Pd(1)–P(1), bond angles, 172.77(12), 170.60 (4)

indicate that the square planar geometry is away from a square plane (Table 2.7). The

angles around Pd lie in the range, 86.10(12)- 97.81(12), which are similar to those

observed in complex 3 {84.84(2)- 95.68(2)}. The ligand is showing disorder of purine

ring in the complex (Figure 2.6). The Pd – N bond distance {2.066(4) Å} is comparable

to 2.093(3) Å bond distance as observed in 1. The Pd S bond distance, 2.4157(14) Å,

is slightly longer than bond distances 2.321(11), 2.345(12) Ǻ found in compound 1. The

Pd – P bond distances, 2.2981(12) and 2.2484(11) Å are unequal. For other complexes

(2, 4-7, 9), similar square planar structures are suggested.

51

Figure 2.5. Structure of [Pd(η2-N

7,S - puS)(dppp)] 8 with numbering scheme.

52

Figure 2.6. Structure of [Pd(η2-N

7, S- puS)(dppp)] 8 showing distortion around Pd.

An attempt to grow crystals of 9 did not succeed and ligand got oxidized during

crystallization (formation of dppbO2 is confirmed by x-ray).

The study shows that bonding modes of pyrimidine-2-thione and purine-6-thione

in palladium (II) reactions are not identical. The mixed bonding mode of pyrimidine-2-

thione in complex 1 is reported first time in literature [1-4]. Pyrimidine - 2 - thiolate is

mainly S - bonded in palladium complexes in 2-5, while purine-6-thiolate is N, S-

chelated in 7-9.

53

Table 2.3: Crystal data for [Pd(η2-N,S- pymS)(η

1-S- pymS) (PPh3)] 1

Empirical formula C26H21N4PPdS2

Formula weight (M) 590.96

Wavelength (Å) 0.71069

Crystal system Monoclinic

Space group P121/n1

Unit cell dimensions

a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

10.774(5)

15.134(5)

15.221(5)

90

96.310(5)

90

Volume (Å3) 2466.8(16)

Z 4

Density calcd (mg/m3) 1.591

Absorption cofficient (mm-1

) 1.009

F(000) 1192

Crystal description Yellow

Crystal size (mm) 0.02 x 0.01 x 0.03

No. of reflections 4450

2Ө range (º) for data collection 0.95 - 12.745

Index range 0 < = h < = 11,0 < = k < = 18,

-18 < = l < = 18

Reflections collected 4703

Data parameter 4450 / 307

Goodness of fit on F2 1.027

R, Rw

0.0314, 0.0743

Largest diff peak and hole (e.Å-3) 0.359 and -0.440

54

Table 2.4: Crystal data for [Pd(η1-S- pymS)2(dppe)] 3

Empirical formula C34H30 N4P2PdS2




Space group P2

Unit Cell dimensions

a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

8.5596(6)

10.5787(8)

35.291(3)

90

90.520(2)

90

Volume (Å3) 3195.4(4)

Z 4



) 0.843

F(000) 1480

Crystal description Yellow prismatic



2Ө range (º) for data collection 1.00 – 13.99

Index range -11 < = h < = 11,-13 < = k < = 13

-34 < = l < = 46


Data Parameter 7420 / 388


R, Rw 0.0506, 0.0758


55

Table 2.5: Crystal data for [Pd(η2-N

7, S- puS)(dppp)] 8

Empirical formula C32H28N4P2PdS



Temperature (K) 100(2)


Space group P21/n


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

10.6827(5)

15.9905(8)

17.0646(8)

90

104.7570(10)

90

Volume (Å3) 2818.9(2)

Z 4

Density calcd. (mg/m3) 1.576

Crystal shape/ colour Plate/ yellow

Absorption coefficient (mm-1

) 0.876

F(000) 1360

Crystal size (mm3) 0.48 0.26 0.19

2θ range (º) for data collection 1.77 – 28.29

Index range -14 < = h < = 14,-21 < = k < = 20,

-22 < = l < = 22


Unique reflections, Rint 6991, 0.0216

Goodness-of-fit on F2 1.254

R, Rw

0.0627, 0.1279

Largest diff. peak and hole (e Å-3

) 3.721 and -3.199

56

Table 2.6: Crystal data for dppbO2.

Empirical formula C28H28O2P2




Crystal system Triclinic

Space group P-1


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

5.8058(3)

8.7901(4)

12.3959(6)

100.276(4)

103.056(4)

104.246(4)

Volume (Å3) 578.67(5)

Z 1

Dcalcd. (mg m-3

) 1.316

Crystal shape/ colour Plate/ pale orange – yellow


) 0.934

F(000) 242

Crystal size (mm3) 0.52 0.48 0.18


Index range -8 < = h < = 8, -13 < = k < = 11,

-15 < = l < = 18



R, Rw

0.0387, 0.09060

57

Table 2.7: Selected bond lengths (Å) and bond angles (º) of 1, 3 and 8.

[Pd(η2-N,S- pymS)(η

1-S- pymS) (PPh3)] 1

Pd – N(3) 2.093(3) N(3)-Pd-P 167.74(8)

Pd –P 2.250(11) N(3)-Pd-S(2) 96.96(8)

Pd – S(2) 2.321(11) P- Pd-S(2) 89.86(5)

Pd – S(1) 2.345(12) N(3)- Pd-S(1) 69.21(8)

P – C(6) 1.820(3) P- Pd-S(1) 103.38(4)

S(1) – C(1) 1.740(3) S(1)- Pd-S(2) 166.02(3)

N(3) – C(1) 1.344(4) C(6)-P-C(12) 106.28(16)

[Pd(η1-S- pymS)2(dppe)] 3

Pd(1)-P(2) 2.2767(6) P(1) Pd(1) P(2) 84.84(2)

Pd(1)-P(1) 2.2773(7) P(2) Pd(1) S(2) 172.91(2)

Pd(1)-S(2) 2.3793(7) P(1) Pd(1) S(2) 90.82(2)

Pd(1)-S(1) 2.3822(7) P(2) Pd(1) S(1) 95.68(2)

S(1) – C(11) 1.745(3) P(1) Pd(1) S(1) 175.04(2)

S(2) – C(21) 1.740(3) S(2) Pd(1) S(1) 89.13(2)

Pd-S(1)-C(11) 97.91(9) Pd-S(2)-C(21) 102.11(9)

58

[Pd(η1-N

7, S- puS) (dppp)] 8

P(1)-Pd(1) 2.2981(12) N(1)-Pd(1)-P(2) 172.77(12)

P(2)-Pd(1) 2.2484(11) N(1)-Pd(1)-P(1) 97.81(12)

Pd(1)-N(1) 2.066(4) P(2)-Pd(1)-P(1) 89.31(4)

Pd(1)-S(1) 2.4157(14) N(1B)-Pd(1)-P(1) 160.0(6)

Pd(1)-S(1B) 2.631(9) N(1)-Pd(1)-S(1) 86.10(12)

Pd(1)-N(1B) 1.899(19) P(2)-Pd(1)-S(1) 87.05(4)

C(31B)-S(1B) 1.758(17) P(1)-Pd(1)-S(1) 170.60(4)

C(31)-S(1) 1.760(5) N(1B)-Pd(1)-P(2) 109.1(6)

C(32)-N(1) 1.368(6) N(1B)-Pd(1)-S(1) 22.0(6)

C(32B)-N(1B) 1.365(18) N(1B)-Pd(1)-N(1) 64.1(6)

C(2)-C(3) 1.393(7) N(1B)-Pd(1)-S(1B) 81.5(6)

C(1)-C(2) 1.402(7) N(1)-Pd(1)-S(1B) 17.48(19)

P(2)-C(16) 1.809(4) P(2)-Pd(1)-S(1B) 168.81(16)

P(1)-C(1) 1.808(5) P(1)-Pd(1)-S(1B) 80.77(16)

C(31)-S(1)-Pd(1) 95.8(2) S(1)-Pd(1)-S(1B) 103.53(16)

C(32)-N(1)-Pd(1) 111.8(3) C(28)-N(1)-Pd(1) 144.6(4)

[dppbO2]

P – O(1) 1.4944(9) O(1)-P-C(3) 110.89(5)

P – C(2) 1.8038(11) C(2)-P-C(9) 106.33(5)

P – C(9) 1.8110(12) C(2)-P-C(3) 105.56(5)

P – C(3) 1.8136(12) C(3)-P-C(9) 105.76

O(1)-P-C(2) 115.17(5) O(1)-P-C(9) 112.47(5)

59

Platinum(II) Complexes

Synthesis of Complexes

Reaction of platinic acid with pyrimidine - 2 - thione (pymSH) with

triphenylphosphine as co-ligand in dry benzene - ethanol mixture in the presence of

triethylamine as a base yielded crystals of stoichiometry, [Pt(η2-N

1,S- pymS)(η

1-S-

pymS)(PPh3)] 10. Since triethylamine was used as a base, the chloride anion was

removed as [Et3NH]+Cl

- salt. Similarly, reaction of platinum(IV) chloride (PtCl4) with

pyrimidine-2-thione and dppm in dry benzene - ethanol mixture in the presence of

triethylamine as a base formed crystals of [Pt(η1- S- pymS)2(dppm)] 11. In situ reduction

of PtIV

to PtII occurs. Other complexes, [Pt(η

1- S- pymS)2(dppe)] 12, [Pt(η

1- S-

pymS)2(dppp)], 13 and [Pt(η1- S- pymS)2(dppb)], 14 were prepared similarly using dppe,

dppp and dppb respectively as co-ligands, using the same procedure.

N

N S

H

H2PtCl6 + 2PPh3 + [Pt(2-N,S- pymS)(1-S- pymS)(PPh3)]

10

PtCl4 + dppm +N

N S

H

[Pt(1-S- pymS)2(dppm)]

11

pymS- = N

N S-1

3

Complexes 10 – 14 are soluble in dichloromethane, chloroform, acetone and

other organic solvents. A bonding view of complexes is shown in scheme 2.3, and it is

clear that all these complexes have square planar geometry. In complex 10, one

deprotonated pymS- is coordinating via

2 - N, S- donor atoms in a chelation mode and

the other one is coordinating via 1- S- donor atom. The coordination mode of pymS

- in

complex 10 is similar to that in complex 1. In complexes, 11 - 14, the deprotonated

pymS- moieties coordinate via

1 - S donor atoms.

60

Pt

PPh3S

N NS

Pt

P

P NS

NS


Scheme 2.3

P P =S N =

10 11 - 14

10-14

N

N S-1

3

Reaction of purine - 6 - thione (puSH2) with platinic acid (H2PtCl6) in a mixture

of dry benzene-ethanol, followed by the addition of triphenylphosphine in the presence of

triethylamine as a base, gave the yellow crystalline complex of stoichiometry, [Pt(η2-

N,S- puS)(PPh3)2], 15. In solution reduction of PtIV

to PtII occurs. In this preparation, the

chloride anion was removed as Et3N+HCl

- salt. Complexes [Pt(η

2-N,S-puS)(dppm)], 16,

[Pt(η2-N,S-puS)(dppp)], 17 and [Pt(η

2-N,S- puS)(dppb)], 18 were prepared similarly,

using dppm, dppp and dppb as co-ligands respectively.

H2PtCl6 + 2PPh3 +N

N

N

N

SH

H

[Pt( 2-N7,S- puS)(PPh3)2]

15

puS2- = N

N

N

N

S-2 7

7

Complexes 15 – 18 are soluble in dimethylsulphoxide and are not soluble in

dichloromethane, chloroform and acetone. Scheme 2.4 gives a brief summary of

61

complexes depicting bonding trend. The x-ray structure of 18 reveals that the geometry of

these complexes is square planar and the deprotonated puS2-

is coordinating via N7-S-

donor atoms in a chelation mode.

Pt

PPh3S

N

Pt

P

P N

S

dppm,16dppp, 17dppb, 18.

Scheme 2.4

P P =S N =

PPh3

15 16-18

N

N

N

N

S-

-

15-18

IR Spectroscopy

The IR spectrum of free pyrimidine - 2 - thione (pymSH) shows a characteristic

peak at 3300 cm-1

due to ν(N – H). The absence of this peak in complexes 10 - 14 shows

deprotonation of the ligand. The ν(C = S) peak of free ligand at 980s cm-1

shows low

energy shift, to 820 - 923 cm-1

in complexes (Table 2.7). The presence of characteristic

ν(P – C) peaks at 1080-1103 cm-1

reveals coordinated tertiary phosphines in all the

complexes. The peaks due to ν(C – N), ν(C – C) and δ(N – H) lie in the region, 1436 -

1560 cm-1

. The absence of ν(N – H) peak (3431 cm-1

) in purine-6-thione complexes 15 -

18 shows deprotonation of the ligand. The ν(C = S) peak of free ligand puSH2 at 868 cm-1

shows low energy shift to 805 - 860 cm-1

, in complexes. The presence of characteristic

ν(P – C) peaks {1110 - 1180 cm-1

} reveals coordinated tertiary phosphines in all the

complexes. The peaks due to ν(C – N), ν(C – C) and δ(N – H) lie in the region, 1440 -

1573 cm-1

. The low energy shift in ν(C = S) peak in complexes 10 - 18 indicates sulphur

coordination in all these complexes.

62



Complexes (N H)

(C H)

(C C) ...

, (C N) ...

(N H)

(C S) (P C)

pymSH 3400br 2910w 1560m, 1460s, 1480s 980br -

10 − 3060w 1537m, 1481s 923m,860w 1087m

11 − 3040w 1558s,1481s 877w,820w 1100m

12 − 3049w 1552s, 1477m 879m,850w 1103m

13 − 3049w 1550s, 1480s 880w,820m 1100m

14 − 3049w 1560s, 1436m 845m,820m 1080m

puSH2 3431s 3095w 1573m,1471s 868s -

15 − - 1560m,1440s 860w,810s 1150m

16 − - 1545m, 1450s 850w 1180m

17 − - 1520s,1460m 805s, 850m 1160m

18 − - 1550m,1445s 850w 1110m

Structures of Pt (II) complexes

The crystal structures of complexes [Pt(η2-N

1,S- pymS)(η

1-S- pymS)(PPh3)] 10,

[Pt(η1-S- pymS)2(dppm)] 11, [Pt(η

2-N

7,S- puS)(dppp)] 17 and [Pt(η

2-N

7,S- puS)(dppb)]

18 are described in this section. Complex 10, 17 and 18 are crystallized in monoclinic

crystal system, and 11 in triclinic crystal system different space groups (Table 2.9 –

2.12).

In complex [Pt(η2-N,S- pymS)(η

1-S- pymS)(PPh3)] 10, two pyrimidine-2-thiolates

(pymS-) and one PPh3 ligands are coordinating to Pt center (Figure 2.7). One pymS

- anion

is chelating via N1, S – donor atoms forming a four membered metallocyclic ring.

The bite angle, N(1)-Pt-S(1), is 68.5(5), which is close to bite angle, N(3)-Pd-S(1),

69.21(8), observed in complex 1 (Table 2.13). The trans bond angles {S(I)-Pt-S(2)

164.2(2), N(1)-Pt-P, 169.1(5)} reveal that the geometry is distorted from a square plane.

In chelated pyrimidine-2-thiolate, the bond angle, Pt-S(1)-C(19) 80.9(7) is shorter than

63

the bond angle, Pt-S(2)-C(23), 104.8(6), in S-bonded pyrimidine-2-thiolate. This

behaviour again indicates different modes of pyrimidine-2-thiolate in complex 1.

The Pt – N and Pt – P bond distances, 2.064(15) Å and 2.231(5) Å respectively

are normal (Table 2.13). The Pt – S bond distances, 2.353(5) Å, 2.324(5) Å, are

somewhat different due to different bonding nature of pyrimidine-2-thiolates. The Pt-S

bond distance is longer in chelated pyrimidine-2-thiolate as compared to S-bonded

pyrimidine-2-thiolate. These Pt – S, Pt – N and Pt – P bond distances are comparable to

the literature values, {Pt – S, 2.301(8) Ǻ; Pt – N, 2.046(23) Ǻ} observed in [Pt2(µ-N,S-

pymS)4(η1-S- pymS)Cl] [125, 126].

Figure 2.7. Molecular structure of [Pt(η2-N

1,S- pymS)(η

1-S- pymS)(PPh3)] 10 with

numbering scheme.

64

The packing diagram of 10 shows double interactions between two molecules in

a 1D chain (Figure 2.8). The sulphur atom of chelated pymS- in one molecule interacts

with H atom of the C4

of non-chelated pymS- in second molecule {CH∙∙∙S, 2.745

Ǻ}(C∙∙∙S, 3.577 Å; C-H∙∙∙S angle, 149.02°) (sum of van der Waals radii of S and H, 3.00

Ǻ [195]). The phenyl ring in first molecule interacts through H atom with the N atom of

non-chelated pymS- in second molecule with CH∙∙∙N contact of 2.692 Ǻ (C∙∙∙N, 3.447 Å;

C-H∙∙∙N angle, 139.29°) (sum of van der Waals radii of N and H, 2.750 Ǻ [195]). The two

1D chains are interacting through the phenyl rings in one chain with the pyrimidyl rings

in other 1D chain {CHpyrimidyl∙∙∙πphenyl , 2.863 Ǻ, CHphenyl∙∙∙πpyrimidyl, 2.789 Ǻ}(C∙∙∙C, 3.793,

3.376 Å; C-H∙∙∙C angle, 134.59°, 165.86°).

Figure 2.8. Packing diagram of [Pt(η2-N

1,S- pymS)(η

1-S- pymS) (PPh3)] 10

On changing monotertiary phosphine to di- tertiary phosphine, the bonding mode of

pyrimidine - 2 - thiolate becomes different. As in complex, [Pt(η1-S-pymS)2(dppm)], 11,

two pyrimidine - 2 - thiolates (pymS-), and one dppm ligand are coordinating to Pt

center. Due to P, P- chelation by dppm, two pyrimidine - 2 - thiolates adopt η1-S-

bonding (Figure 2.9). The two trans, P – Pt – S, bond angles, {177.47(3), 175.27(3)}

reveal that the geometry is less distorted from a square plane (Table 2.12), as compared

65

to that observed in complexes 1 and 10. The angles around Pt center lie in the range,

73.73(3) – 103.96(3).

The Pt – S bond distances, 2.3445(8) Å and 2.3479(8) Å, are nearly equal, and

likewise Pt – P bond distances, 2.2683(8), 2.2727(8) Å, are comparable (Table 2.13).

These bond distances are comparable with other complexes, Pd – S, 2.3793(7), 2.3822(7)

Å, Pd – P, 2.2767(6), 2.2773(7) Å observed in 3; Pt – S, 2.301(8); Pt – N, 2.046(23) Ǻ in

[Pt2(µ-N,S-pymS)4(η1-S- pymS)Cl] [125, 126].

Figure 2.9. Molecular structure of [Pt(η1-S- pymS)2(dppm)] 11 with numbering

scheme.

The packing diagram of complex 11 shows that two chains are stacked on one

another, interacting through both nitrogen and sulphur of pyrimidine - 2 - thiolate

(Figure 2.10). The nitrogen of one pyrimidyl group in one ID chain interacts with H

atom of phenyl ring in another 1D chain {CH∙∙∙N, 2.545 Å}(C∙∙∙N, 3.388 Å; C-H∙∙∙N

angle, 136.06°) and sulphur of the other pyrimidyl ring in same molecule also interacts

with the H atom of phenyl ring in another 1D chain {CH∙∙∙S, 2.970 Å}(C∙∙∙S, 3.740 Å; C-

H∙∙∙S angle, 139.15°) (sum of the van der Waals radii of N and H, 2.750 Ǻ and S and H,

3.00 Ǻ [195]). The N atom of the pyrimidyl ring (whose S - atom is also interacting)

66

shows a contact with H of the phenyl ring in another molecule {CH∙∙∙N, 2.638 Å}(C∙∙∙N,

3.466 Å; C-H∙∙∙N angle, 163.14°). This contact is again less than the sum of their van der

Waals radii of N and H {2.750 Ǻ}.

Figure 2.10. Packing diagram of [Pt(η1-S- pymS)2(dppm)] 11

Purine - 6 - thiolate, behaves differently with tertiary phosphines co-ligands as

compared with pyrimidine - 2 - thione. In [Pt(η2-N,S-puS)(dppp)] 17, only one purine-6-

thiolate is bonded (Figure 2.11). In contrast, in complex 11 two pyrimidine-2-thiolates

are bonded through sulphur only. Despite P, P chelation by dppp, the thio-ligand is in

N, S- chelation mode. The two trans, N–Pt–P(1) and S–Pt–P(2) bond angles, 173.5(4),

172.13(8) reveal that the geometry is less distorted from a square plane than in

complexes 10 and 11 (Table 2.13). All the four bond angles around Pt lie in the range,

86.4(4)- 96.1(4), which is quite similar to that observed in complex 11.

The Pt – S, 2.414(3) bond distance is somewhat longer while Pt – P, 2.243(3),

2.286(3) Å bond distances (Table 2.13) are comparable to those observed in complex 11

{Pt– S; 2.3445(8) Å and 2.3479(8) Å, Pt– P, 2.2683(8) Å and 2.2727(8) Å}. The Pt – N

bond length is 2.108(12) Å, which is somewhat longer than that observed in complex

10.

67


7,S- puS)(dppp)] 17 with numbering

scheme.

The packing diagram of this complex shows that nitrogen atom of five membered

ring in purine-6-thione interacts with H atom of the phenyl ring {CH∙∙∙N, 2.588 Å}(C∙∙∙N,

3.387 Å; C-H∙∙∙N angle, 148.72°) (sum of the van der Waals radii of N and H atoms,

2.750 Ǻ [195]). The H atom of phenyl ring in one complex is interacting with C atom of

another unit showing CH∙∙∙π interactions {CHphenyl ∙∙∙πphenyl = 2.783 Ǻ} (C∙∙∙C, 3.467 Å;

C-H∙∙∙C angle, 131.22°) (Figure 2.12). This generates a 1D polymer. The same N atoms

of one 1D chain interact with H atoms of the phenyl rings of another 1D chain, {CH∙∙∙N,

2.633 Å}(C∙∙∙N, 3.334 Å; C-H∙∙∙C angle, 132.66°). This contact is also less than the sum

of the van der Waals radii of N and H atoms {2.750 Ǻ}[195].

68


7,S- puS)(dppp)] 17.

In [Pt(η2-N, S-puS)(dppb)] 18, only one purine - 6 - thiolate is bonded and in

contrast in complex 11, two pyrimidine - 2 - thiolates are bonded through sulphur only

(Figure 2.13). Despite P, P chelation by dppb, the ligand is also in N, S- chelation mode

like that in 17. Two trans, N(1)–Pt(1)–P(1) and S(4)–Pt(1)–P(2) bond angles,

165.4(3),175.96(8) reveal that the geometry is less distorted from a square plane than in

complexes 10 and 11 (Table 2.13). All the four bond angles around Pt lie in the range,

85.18(7)- 96.38(19), which is quite similar to that observed in 11 and 17.

The Pt – S, 2.385(2) Å distance is shorter than in 17 {Pt– S; 2.414 (3) Å}, but

comparable to that in 11. The Pt – P, 2.256(2), 2.277(2) Å bond distances are comparable

to those observed in 11 and 17. The Pt – N bond length, 2.119(6) Å is somewhat longer

than in 10, but comparable to that in 17.

69


7,S- puS)(dppb)] 18 with numbering

scheme.

The packing diagram of 18 shows only intermolecular interactions (Figure 2.14).

Two H atoms of CH2 of dppb in one molecule interacts with C atoms of phenyl rings in

another molecules. The H atom of the same molecule interacts with C atom of the

pyrimidyl ring {CHphenyl ∙∙∙ πpyrimidyl = 2.869 Ǻ} (C∙∙∙C, 3.587 Å; C-H∙∙∙C angle, 149.55°)

[195]. This generates a 1D polymer. The molecules in 1D chain interacts with other 1D

chain with similar CH∙∙∙π interactions {CH2(dppe) ∙∙∙ πphenyl = 2.768, 2.874 Ǻ} (C∙∙∙C, 3.724,

3.702 Å; C-H∙∙∙C angle, 142.52, 146.82°) and forming a 2D network.

70


7,S- puS)(dppb)] 18.

From the study of these complexes, it is clear that the bonding mode of pyrimidine - 2

- thione and purine-6-thione is not similar. In pyrimidine - 2 - thiolate complexes, the

ligand is mainly η1-S- bonded, while in purine - 6 - thiolate complexes, it is N

7,S-

chelated. It is noted that similar trend is observed for both the ligands in platinum(II) and

palladium(II) complexes.

71

Table 2.9: Crystal data for [Pt(η2-N,S- pymS)(η

1-S- pymS)

(PPh3)] 10.

Empirical formula C26 H21N4PPtS2




Space group P21/n


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

10.791(1)

15.126(2)

15.232(1)

90

96.51(1)

90

Volume (Å3) 2470.2(4)

Z 4



) 5.937

F(000) 1320

Crystal description Yellow



Ө range (°) for data collection 0.95 - 12.5

Index range 0<=h<=10, 0<=k<=17

-18<=l<=17


Data Parameter 4148 / 307


R, Rw 0.0730, 0.2011


72

Table 2.10: Crystal data for [Pt(η1-S- pymS)2(dppm)] 11.

Empirical formula C33H28N4P2PtS2




Space group P1


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

8.8941(11)

11.1734(14)

15.736(2)

84.493(2)

83.537(2)

80.810(2)

Volume (Å3) 1529.0(3)

Z 2



) 4.861

F(000) 788

Crystal description Colorless square plates



Ө range (°) for data collection 1.09 – 14.35

Index range -11<=h<=11,-14<=k<=14,

-19<=l<=21

Reflection collected 12030



R, Rw

0.0293, 0.0731


73

Table 2.11: Crystal data for [Pt(η2 - N

7,S- puS)(dppp)] 17.

Empirical formula C32H27N4P2PtS




Space group P121/n1


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

10.7720(3)

16.0467(4)

17.2701(4)

90.00

104.395(2)

90.00

Volume (Å3) 2891.50(13)

Z 4



) 11.028

F(000) 1484

Crystal description Yellow plates



2Ө range (°) for data collection 5.05 – 77.83

Index range -13<=h<=13,-20<=k<=20,

-14<=l<=21


Data parameter 6035/361


R, Rw

0.0976, 0.1020

74

Table 2.12: Crystal data for [Pt(η2 - N

7,S- puS)(dppb)] 18.

Empirical formula C33H30N4P2PtS




Space group P21


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

10.9463(4)

13.1054(5)

11.8560(4)

90.00

99.6290(10)

90.00

Volume (Å3) 1676.85(11)

Z 2



) 4.369

F(000) 760



Ө range (°) for data collection 0.87 – 12.5

Index range -13<=h<=13,-15<=k<=15,

-9<=l<=14


Data parameter 5521/370


R, Rw

0.0348, 0.1083

75

Table 2.13: Selected bond engths (Å) and bond angles (º) of 10, 11, 17 and 18.


1-S- pymS)(PPh3)] 10.

Pt - N(1) 2.064(15) N(1)-Pt-P(1) 169.1(5)

Pt – P(1) 2.231(5) N(I)-Pt-S(2) 95.9(5)

Pt- S(1) 2.353(5) P(1)- Pt-S(2) 91.26(18)

Pt - S(2) 2.324(5) N(1)- Pt-S(1) 68.5(5)

P(1) – C(1) 1.837(18) P(1)- Pt-S(1) 103.94(19)

S(1) – C(19) 1.73(2) S(1)- Pt-S(2) 164.2(2)

N(1) – C(19) 1.34(3) C(7)-P(1)-C(1) 107.2(9)

Pt-S(2)-C(23) 104.8(6) Pt -S(1)- C(19) 80.9(7)

[Pt(η1-S- pymS)2(dppm)] 11

Pt-P(2) 2.2683(8) P(2)-Pt-P(1) 73.73(3)

Pt-P(1) 2.2727(8) P(2)-Pt-S(1A) 177.47(3)

Pt-S(1A) 2.3445(8) P(1)-Pt-S(1B) 175.27(3)

Pt-S(1B) 2.3479(8) S(1A)-Pt-S(1B) 79.35(3)

P(1) – C(1) 1.849(3) C(1A)-S(1A)-Pt 113.41(11)

S(1A)-C(1A) 1.742(3) C(1B)-S(1B)-Pt 113.15(11)

P(2) –Pt-S(1B) 103.02(3) P(1)-Pt-S(1A) 103.96(3)

[Pt(η2-N

7,S- puS)(dppp)] 17

Pt-P(2) 2.286(3) P(2)-Pt-P(1) 90.20(11)

Pt-P(1) 2.243(3) P(1)-Pt-N4A 173.5(4)

Pt-S(1) 2.414(3) P(2)-Pt-N4A 96.1(4)

Pt-N4A 2.108(12) N4A-Pt-S 86.4(4)

P(1) – C(1) 1.786(13) P(1)-Pt-S 87.62(11)

P(1)-C(7) 1.885(12) P(2)-Pt-S 172.13(12)

76

[Pt(η2-N

7,S- puS)2(dppb)] 18

Pt(1)-P(2) 2.277(2) P(2)-Pt(1)-P(1) 93.86(7)

Pt(1)-P(1) 2.256(2) P(1)-Pt(1)-N(1) 165.4(3)

Pt(1)-S(4) 2.385(2) P(2)-Pt(1)-N(1) 96.38(19)

Pt(1)-N(1) 2.119(6) N(1)-Pt(1)-S(4) 85.30(19)

P(1) – C(1) 1.831(9) P(1)-Pt(1)-S(4) 85.18(7)

P(1)-C(7) 1.181(7) P(2)-Pt(1)-S(4) 175.96(8)

77

NMR Spectroscopy (PdII

and PtII

complexes)

NMR spectral data (1H,

13C and

31P NMR) of pyrimidine - 2 – thione and purine -

6 - thione complexes of PdII/Pt

II are described in this section.

Pyrimidine-2-thione complexes

1H NMR spectral studies

The -N1H- proton of pymSH appears at δ, 13.4 ppm in dmso - d

6 [154]. The

absence of this peak in complexes revealed that the ligand is acting as anion, coordinating

either through N, S- or S- donor atoms (V, Va, Vb). The H4, H

6 protons of free ligand

were unresolved and appeared at δ, 8.59 ppm (Table 2.14). In palladium (II) complex 1,

these signals were resolved and appeared as a set of two peaks at δ, 8.58, 7.72 (H4) and

8.14, 7.71 (H6) ppm. The H

5 signal in free ligand appeared at δ, 7.10 ppm. But in

complex 1, it appeared upfield at δ, 7.26, 6.67 ppm. The chelated pyrimidine - 2 - thione

showed H4, H

6, H

5 signals at δ, 7.72, 7.71, 6.67 ppm respectively (Va), while η

1 - S -

bonded pyrimidine - 2 - thione showed these signals at δ, 8.58, 8.14, 7.26 ppm (Vb)

respectively. In complexes, 2 - 5, the H5, H

6, H

4 signals lie in the range, δ, 6.64 – 8.58

ppm and are upfield. This behaviour is quite similar to that in analogous complexes

[47,48]. The o-, m- and p- hydrogens in PPh3 and other P-Ph moieties of diphosphines,

appeared as mutliplets in the ranges; 7.60 - 7.88 (o-H); 7.49 - 7.83 (m-H) and 7.41-7.73

(p-H).

N

N S1

2

3

4

5

6

H

-H+N

N S

M

N

N S

M

or

V Va Vb

In Pt complex 10, a set of two signals appeared at δ, 8.81, 8.58 (H4); 8.48, 8.44

(H6) and 7.10, 6.90 (H

5) (Table 2.14). The signals at δ, 8.58, 8.44 and 6.90 for H

4, H

6, H

5

78

revealed η2-N,S-bonding, while these signals at δ, 8.81, 8.58, 6.9 ppm revealed η

1-S-

bonding. The signals of complexes 11 - 14 indicate only η1-S- bonding and are upfield.

This behaviour is again similar to the pyridine - 2 - thione complexes reported in

literature [47, 48]. The o-, m- and p- hydrogens in PPh3 and other P-Ph moieties of

diphosphines, appeared as mutliplets in the ranges; 7.33 – 7.86 (o-H); 7.60 – 7.73 (m-H)

and 7.49 – 7.73 (p-H).

Table 2.14: 1H NMR spectra (δ, ppm) of Pd(II) and Pt(II) complexes of pyrimidine-2-

thione.

H4 H

6 H

5 Mode

pymSH 8.59 8.59 7.10 η1 – S


1-S-

pymS)(PPh3)] 1

8.58

7.72

8.14

7.71

7.26

6.67

η1 – S

η2 – N, S


8.58 8.18 7.09 η1 – S

[Pd(η1-S-pymS)2(dppe)] 3

8.58 8.58 7.09 η1 – S

[Pd(η1-S- pymS)2(dppp)] 4

8.12 8.11 6.64 η1 – S

[Pd(η1-S- pymS)2(dppb)] 5

8.13 8.13 6.7 η1 – S


1-S-

pymS)(PPh3)] 10

8.81

8.58

8.48

8.44

7.1

6.9

η1 – S

η2 – N, S

[Pt(η1-S-pymS)2(dppm)] 11

8.58 8.58 7.1 η1 – S

[Pt(η1-S- pymS)2(dppe)] 12

8.58 8.58 7.09 η1 – S

[Pt(η1-S- pymS)2(dppp)] 13

8.02 7.13 6.50 η1 – S

[Pt(η1-S- pymS)2(dppb)] 14

8.58 8.15 7.1 η1 – S

N

N S1

2

34

5

6

H

HH

H

79

31P NMR spectral studies

Complex 1 showed one 31

P NMR signal, at δ = 33.6 ppm. Each of complexes 2 - 5,

showed two signals (Table 2.15). Similar is behaviour in platinum complexes except for

complex 11 which showed one signal at δ, -6.44 ppm. The presence of two signals

reveals,

1. that two P atoms are magnetically nonequivalent.

2. that there might be an equilibrium due to competitive ligation as shown below

(VIa-VIc).

M

P

P NS

M

P

P

NS

NSNS

M

PP NS

N SCDCl3 CDCl3

11 1

12 222

2

2

11

VIa VIb VIc

The spectra showed variable intensity of signals. The variable intensity points to second

possibility of equilibrium between various species (VIa-VIc). The chelated diphosphine

31P NMR signals appeared at low field, 30.9 - 33.9 ppm, while non-chelated diphosphine

signals lie in the range, 2.8 - 28.7 ppm. The coordination shifts are quite significant and

reveal relatively strong M-P bonding (M = Pd(II), Pt(II)). The behaviour of Pt complex

11, is similar to 1 and 10. In 11, there appears fast equilibrium between VIb and VIc.

M

P

P

NS

NS

M

PP NS

N SCDCl3

11 1

12 22

2

VIb VIc

80

Table 2.15: 31

P NMR spectra (δ, ppm) of Pd(II) and Pt(II) complexes of

pyrimidine - 2 – thione.

Complex δP Δδ(δcomplex – δligand)


1-S-

pymS)(PPh3)] - 1

33.6 38.3


30.9, 25.7 35.6, 30.4

[Pd(η1-S-pymS)2(dppe)] 3

33.2, 28.7 37.9, 33.4

[Pd(η1-S-pymS)2(dppp)] 4

33.0, 28.3 37.7, 33.0

[Pd(η1-S-pymS)2(dppb)] 5

33.2, 2.8 37.9, 7.5

[Pt(η2-N,S-pymS)(η

1-S-

pymS)(PPh3)] - 10

29.8 34.5

[Pt(η1-S-pymS)2(dppm)]11

-6.4 -1.7

[Pt(η1-S-pymS)2(dppe)] 12

33.9, 42.0 38.6, 46.7

[Pt(η1-S-pymS)2(dppp)] 13

33.4, 28.4 37.1, 33.1

[Pt(η1-S-pymS)2(dppb)] 14

33.1, 2.8 37.8, 7.5

81

13C -NMR spectral studies

The 13

C NMR spectra of complexes, 1 - 4 and 10 -14 have been obtained and

data are shown in Table 2.16. The C2 signals appeared at low field in the range, δ, 179.0 -

195.0 ppm. Similarly, the signals due to C4 and C

6, either merged at the same position, or

were resolved. The signal due to C5 appeared as a single peak at high field in the range, δ,

96.6 - 118.2 ppm. The P-Ph moieties showed signals which lie in the range, δ,128.4 -

133.9 ppm. The CH2 signals appeared as single or double peaks at, δ, 45.79 - 47.96 ppm.

Complex C2 C

4, C

6 C

5 P-Ph moieties

pymSH [154] 181.4 158.6, 154.6 119.1


1-S-

pymS)(PPh3)] 1

185.0 155.6 96.6 128.45-138.21

[Pd(η1-S-pymS)2(dppm)] 2 188.7 163.9 113.9 128.39-132.65

[Pd(η1-S-pymS)2(dppe)] 3 185.0 155.7 114.6 128.44-133.07

[Pd(η1-S-pymS)2(dppp)] 4 195.0

179.0

155.6, 155.6

150.7, 140.1

118.1

114.6

128.46-133.09

[Pt(η2-N,S-pymS)(η

1-S-

pymS)(PPh3)] 10

_ 157.9 _ 128.21-134.2

[Pt(η1-S-pymS)2(dppm)]11 185.0 157.9 118.2 128.4-133.9

[Pt(η1-S-pymS)2(dppe)] 12 185.0 157.9 _ 128.4-132.13

[Pt(η1-S-pymS)2(dppp)] 13 _ 160.3 _ 128.63-131.8

[Pt(η1-S-pymS)2(dppb)] 14 _ 157.9 118.2 128.37-133.04

N

N S1

2

34

5

6

H

HH

H

82

Purine -6-thione complexes

NMR spectral studies (1H and

31P NMR) of complexes 6 - 9, 15 - 18 are

discussed in this section.


The H2 proton signal of purine ring shifts downfield or upfield in complexes (Table 2.17).

The H8 proton signals generally showed downfield shifts in complexes relative to the free

ligands. The phenyl proton signals of phosphines were multiplets found in the broad

range, 6.68 – 7.88 ppm.

Table 2.17: 1H – NMR spectra peaks (δ, ppm) of purine-6-thione

complexes (6 - 9; 15 - 18)

Complex H8 H

2 P-Ph moieties

puSH2 7.75 7.10

[Pd(η2-N

7,S-puS)(PPh3)2] 6

- 7.20 7.29-7.68

[Pd(η2-N

7,S-puS)(dppm)] 7

8.96 8.54, 8.44 7.47-7.88

[Pd(η2-N

7,S- puS)(dppp)] 8

8.45 6.61 7.34-7.72

[Pd(η2-N

7,S- puS)(dppb)] 9

9.01 8.50,8.46 7.43-7.74

[Pt(η2-N

7, S-puS)(PPh3)2] 15

8.50 7.40 7.47-7.66

[Pt(η2-N

7, S-puS)(dppm)] 16

7.22 6.50 6.68-6.90

[Pt(η2-N

7, S- puS)(dppp)] 17

8.50 6.50 7.35-7.70

[Pt(η2-N

7, S- puS)(dppb)] 18

8.50 6.64 7.37-7.66

N

N

N

N

S6 7

8

9

1

23

4

5

H

H

H

H

83


The 31

P NMR spectral data of purine - 6 - thione complexes are shown in Table

2.18. Since P atoms are trans to N and S atoms, the environments around P nuclei are not

equivalent. This is reflected in the appearance of more than one signal in the 31

P spectra.

This phenomenon is more prevalent in PdII complexes. In Pt

II complexes (15 - 18), there

was only one signal shown by each complex. It is possible, two types of environments in

PtII complexes are not resolved.

Table 2.18: 31

P NMR spectra peaks (δ, ppm) of purine - 6 - thione complexes


[Pd(η2-N

7,S-puS)(PPh3)2] 6

26.5, -8.29 31.2, -3.6

[Pd(η2-N

7,S- puS)(dppm)] 7

27.8, 22.70 32.4, 27.40

[Pd(η2- N

7,S- puS)(dppp)] 8

37.31, 34.45, 13.9 42.0, 39.15, 18.6

[Pd(η2-N

7,S- puS)(dppb)] 9

32.08, 29.35, 9.39 36.78, 34.05, 14.09

[Pt(η2-N

7, S-puS)(PPh3)2] 15

31.24 35.94

[Pt(η2-N

7, S-puS)(dppm)] 16

32.46 37.16

[Pt(η2-N

7, S- puS)(dppp)] 17

26.98 31.68

[Pt(η2-N

7, S- puS)(dppb)] 18

34.58 39.28

84

Ruthenium (II) Complexes

Synthesis

Reaction of [RuCl2(PPh3)3] [196] with pyrimidine - 2 - thione (pymSH) in 1 : 2

molar ratio, using triethylamine as a base, in dry benzene, gave crystals of stoichiometry,

[Ru(η2-N,S-pymS)2(PPh3)2] 19. The chloride anion was removed as Et3N

+HCl

- salt. It

was prepared under dry and oxygen free N2 to avoid oxidation of Ru2+

→ Ru3+

.

Complexes [Ru(η2-N,S-pymS)2dppm)] 20, [Ru(η

2-N,S-pymS)2(dppp)] 22 and [Ru(η

2-

N,S-pymS)2(dppb)] 23 were prepared similarly using [RuCl2(dppm)2], [RuCl2(dppp)2]

and [Ru2Cl4(dppp)3] [197] as starting materials under N2 atmosphere.

The dppe complex has been prepared indirectly. Thus reaction of [Ru(η2-N,S-

pymS)2(PPh3)2] with 1,2-bis(diphenylphosphino)ethane (dppe) in 1 : 1 molar ratio in dry

toluene yielded a crystalline mass of stoichiometry, [Ru(η2-N,S-pymS)2(dppe)] 21 under

N2 atmosphere. Here PPh3 was replaced by dppe due to chelation effect. Direct reaction

of RuCl2(dppe)2 did not succeed.

RuCl2(PPh3)3 + 2N

N S

H

[Ru( 2-N,S-pymS)2(PPh3)2] + 2Et3N+HCl-

19

pymS- =N

N S_

Et3N

- PPh3

RuCl2(L-L)2 + 2N

N S

H

[Ru( 2-N,S-pymS)2(L-L)] + 2Et3N+HCl-

20, 22

Et3N

- (L-L)

Ru2Cl3(dppb)3 + 2N

N S

H

[Ru( 2-N,S-pymS)2(dppb)] + 2Et3N+HCl-

23

Et3N

-2dppb

L-L = dppm (20) dppp (22)

dppb (23)

85

[Ru( 2-N,S-pymS)2(dppe)]

21

Ru(pymS)2(PPh3)2 + dppeEt3N

- 2PPh3

Complexes 19 – 23 are soluble in dichloromethane, chloroform and acetone.

Scheme 2.5 gives a bonding view of complexes. The x-ray structures of 19 and 22 have

shown that these complexes of Ru(II) have octahedral geometries. The deprotonated

pyrimidine-2-thiolate is coordinating via 2 - N, S- donor atoms in a chelation mode.

IR Spectroscopy

The IR spectrum of free pyrimidine - 2 - thione shows a characteristic peak at 3300

cm-1

due to ν(N – H). The absence of this peak in complexes 19 - 23 shows deprotonation

of the ligand. The ν(C = S) peak of free ligand pymSH at 980 cm-1

shows low energy

shifts to 800-871 cm-1

in complexes (Table 2.19). The presence of characteristic ν(P – C)

peaks in the range 1090-1095 cm-1

reveals the presence of coordinated phosphines in all

these complexes. The peaks due to ν(C – N), ν(C – C) and δ(N – H) lie in the region,

1480 - 1560 cm-1

.

PPh3

PPh3

S

Ru

P

S

N

N

P

S

Ru

S

N

N


Scheme 2.5

P P =S N =

19 20 - 23

N

N S-

19-23

86

The low energy shift in ν(C = S) peak after complexation, shows sulphur

coordination in all these complexes. The absence of ν(N – H) peak in the complexes,

reveals anionic pymS- and probably nitrogen is also coordinating.



Complexes (N H)

(C H)

(C C) ...

, (C N) ..., (N H)

(C S) (P C)

pymSH 3300br 2910 1560s, 1460s,1480s 980br

19 3060w 1560s,1480 850m 1090m

20 3040w 1560s,1480 840w,790w 1090m

21 3040w 1560m,1480 850w,800s 1090m

22 3049w 1560s,1480 856m,800s 1095m

23 3049w 1558s,1480 871m,791m 1095m

Structures of Ru(II) complexes

The crystal structures of [Ru(η2-N, S- pymS)2(PPh3)2] 19 and [Ru(η

2-N, S-

pymS)2(dppp)] 22 are described in this section. Complexes 19 and 22 are crystallized in

triclinic system with space groups P-1 (Table 2.20 - 2.21).

In complex 19, RuII is coordinated to two triphenylphosphine units and two

pyrimidine - 2 - thiolate units in a cis position (Figure 2.15). The sulphur atoms in two

pyrimidine - 2 - thiolates occupy trans position with, S(1) – Ru(1) – S(2) bond angle of

153.02º, which is close to 154.7º, that was observed in [Ru(η2 - N, S- pyS)2(PPh3)2] as

reported in literature [32] (Table 2.22). The N(21) – Ru – N(11) bond angle of 83.46º, is

longer than, 80.9º, which was observed in [Ru(η2 - N,S- pyS)2(PPh3)2] [32], while P(2) –

Ru(1) – P(1) bond angle, 96.07º, is comparable (96.8º).

The bond distances, Ru – P, 2.3266(7), 2.3167(7) Å, Ru – S, 2.4256(8),

2.4413(8) Å and Ru – N, 2.119(2), 2.106(2) Å are comparable to Ru – P, 2.332, 2.319 Å;

87

Ru – S, 2.435 Å and Ru – N, 2.123 Å, bond distances observed in related complex

[Ru(η2-N,S- pyS)2(PPh3)2] [32].

Figure 2.15. Molecular structure of [Ru(η2-N, S- pymS)2(PPh3)2] 19 with numbering

scheme

The packing diagram of 19 shows only intermolecular interactions (Figure 2.16).

The sulphur atom of pyrimidine-2-thiolate in one molecule shows an interaction with

88

the hydrogen atom of the phenyl ring in second molecule {CH∙∙∙S, 2.870 Å}(C∙∙∙S, 3.756

Å; C-H∙∙∙S angle, 157.64°) (sum of van der Waals radii of S and H, 3.00 Ǻ [195]). The

nitrogen of one pyrimidyl ring is interacting with hydrogens in the adjasant pyrimidyl

ring {CH∙∙∙N = 2.688 and 2.717 Å} (C∙∙∙N, 3.321, 3.314 Å; C-H∙∙∙C angle, 124.58,

122.62°) (sum of their van der Waals radii of N and H, 2.750 Ǻ [195]). These

interactions constitute a 1D polymer. The two 1D chains are interacting through phenyl

rings {CH∙∙∙π, 2.778, 2.850, 2.702 Ǻ}(C∙∙∙C, 3.565, 3.640, 3.634 Å; C-H∙∙∙C angles,

132.79, 152.93, 142.35°) forming a 2D polymer.

Figure 2.16. Packing diagram of [Ru(η2-N,S- pymS)2(PPh3)2] 19.

On changing a monotertiary phosphine to di- tertiary phosphine, no change is

observed in the coordination mode of the pyrimidine-2-thiolate. In complex [Ru(η2-N,S-

pymS)2(dppp)] 22, RuII is coordinated to two P atoms of dppp and N, S atoms of two

pyrimidine - 2 - thiolate ligands (Figure 2.17). Despite P, P chelation by dppp, the

pyrimidine - 2 - thiolate is bonded through N, S- chelation mode unlike complexes 3 and

11. The S atoms of pyrimidine - 2 - thiolate occupy trans positions with S(1A) – Ru –

S(1B) bond angle of 154.54(3)º which is slightly longer, 153.02º, than that observed in

89

19 (Table 2.22). The S – Ru – S angles lie in the range, 153.9 – 155.6º, similar to the

literature trends [33, 35, 36]. The bond angle, N(1A) – Ru – N(1B), 83.38(9)º, in 22 is

close to the bond angle, 83.46 (9)º observed in 19, but the bond angle, P(1) – Ru – P(2),

89.57(3)º is smaller than the bond angle, 96.07(3)º in 19 due to chelation of dppp. The

bite angle, N – Ru – S, 67.32(7)º remains constant both in 22 and 19.

The Ru – P bond distances, 2.2603(8) Å, 2.2713(7) Å are shorter than 2.3266(7),

2.3167(7) Å bond distances observed in 19. The Ru – S = 2.4187(7) Å, 2.4325(7) Å and

Ru – N = 2.131(2) Å, 2.134(2) Å bond distances are comparable to bond distances in 19

{Ru – S = 2.4256(8), 2.4413(8) Å and Ru – N = 2.119(2), 2.106(2) Å}. These bond

distances are comparable to the literature values [33, 35, 36].

Figure 2.17. Molecular structure of [Ru(η2-N, S- pymS)2 (dppp)] 22 with numbering

scheme.

90

The packing diagram of 22 shows that the C5 hydrogen of chelated pyms

- in one

molecule interacts with phenyl ring of second molecule {CH∙∙∙π, 2.872 Å} (C∙∙∙C, 3.701

Å; C-H∙∙∙C angles, 134.39°) (Figure 2.18). These weak interactions make a 1D chain.

The two 1D chains are interacting through S and N atoms in one chain and hydrogens of

the phenyl rings in another chain {CH∙∙∙S = 2.795 Å, CH∙∙∙N, 2.704 Å} (C∙∙∙S, 3.668 Å;

C∙∙∙N, 3.408 Å; C-H∙∙∙S angle, 152.92°; C-H∙∙∙N angle 151.42°) (sum of van der Waals

radii of S and H, 3.00 Ǻ and N and H, 2.750 Ǻ [195]). Two 1D chains are also interacting

through CH∙∙∙π interactions of 2.822 Ǻ between the phenyl rings (C∙∙∙C, 3.559 Å; C-

H∙∙∙C angles, 154.99°). These interactions generate a zig-zag 2D polymer.

Figure 2.18. Packing diagram of [Ru(η2-N, S- pymS)2(dppp)] 22.

91

Table 2.20: Crystal data for [Ru(η2-N, S- pymS)2(PPh3)2] 19.

Empirical formula C47H39N4P2RuS2




Space group P-1 (No. 2)


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

11.0610(8)

12.2203(14)

17.1748(16)

69.564(9)

85.075(7)

68.943(8)

Volume (Å3) 2028.0(3)

Z 2



) 5.142

F(000) 910

Crystal description Brown prismatic



2Ө range (°) for data collection 2.60 – 32.49

Index range -1<=h<=12,-13<=k<=14,

-20<=l<=20




R, Rw 0.0324, 0.0800

Largest diff peak and hole (e.Å-3) 0.489 and –1.079

92

Table 2.21: Crystal data for [Ru(η2-N, S- pymS)2(dppp)] 22.

Empirical formula C35H32N4P2 RuS2





Space group P-1


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

11.0603(7)

11.2473(7)

14.3329(9)

90.0330(10)

105.1230(10)

111.1880(10)

V (Å3) 1595.95(17)

Z 2

Density calcd. (mg m-3

) 1.531


) 0.755

F(000) 752

Crystal description Yellow plate

Crystal size (mm3) 0.15 x 0.30 x 0.45

2θ range (º) for data collection 1.95 - 28.31

Index range -14<=h<=14,-14<=k<=15,

-17<=l<=19


Unique reflections, Rint 7484,0.0583


R, Rw

0.0422, 0.1070


) 1.201 and -0.726

93

Table 2.22: Selected bond lengths (Å) and bond angles (º) in 19 and 22.

[Ru(η2-N, S- pymS)2(PPh3)2] 19

Ru(1)-N(11) 2.119(2) N(11)-Ru(1)-S(1) 67.21(7)

Ru(1)-N(21) 2.106(2) N(11)-Ru(1)-S(2) 92.26(7)

Ru(1)-P(1) 2.3266(7) N(21)-Ru(1)-S(1) 92.40(7)

Ru(1)-P(2) 2.3167(7) N(21)-Ru(1)-S(2) 67.03(7)

Ru(1)-S(1) 2.4256(8) S(1)-Ru(1)-S(2) 153.02(3)

Ru(1)-S(2) 2.4413(8) N(21)-Ru(1)-N(11) 83.46(9)

Ru(1)-N(11) 2.119(2) N(11)-Ru(1)-P(1) 170.91(6)

N(21)-Ru(1)-P(2) 172.17(7) N(11)-Ru(1)-P(2) 90.56(6)

P(2)-Ru(1)-P(1) 96.07(3) N(21)-Ru(1)-P(1) 90.44(7)

[Ru(η2-N, S- pymS)2(dppp)] 22

Ru-N(1A) 2.131(2) N(1A)-Ru-N(1B) 83.38(9)

Ru-N(1B) 2.134(2) N(1A)-Ru-P(1) 164.58(7)

Ru-P(1) 2.2603(8) N(1B)-Ru-P(1) 95.30(7)

Ru-P(2) 2.2713(7) N(1A)-Ru-P(2) 93.09(7)

Ru-S(1A) 2.4186(7) N(1B)-Ru-P(2) 173.41(7)

Ru-S(1B) 2.4325(7) P(1)-Ru-P(2) 89.57(3)

P(1)-C(1) 1.842(3) N(1A)-Ru-S(1A) 67.79(7)

P(2)-C(3) 1.840(3) N(1B)-Ru-S(1A) 93.56(7)

S(1A)-C(5A) 1.737(3) P(1)-Ru-S(1A) 97.04(3)

P(2)-Ru-S(1B) 107.41(3) P(2)-Ru-S(1A) 90.24(3)

S(1A)-Ru-S(1B) 154.54(3) N(1A)-Ru-S(1B) 92.50(7)

P(1)-Ru-S(1B) 101.20(3) N(1B)-Ru-S(1B) 67.32(7)

94

NMR Spectroscopy (RuII

Complexes)

NMR spectral data (1H,

13C and

31P NMR) of pyrimidine - 2 - thione complexes of

RuII are discussed in this section.


Ruthenium(II) complexes did not show –N1H- proton signal {δ,13.4 ppm in dmso-

d6 [154]} and thus pymSH is acting as anion pymS

- (VII, VIIa).

N

N S1

2

3

4

5

6

H

-H+N

N S

M

VII VIIa

The H4, H

6 protons of the free ligand, pymSH, were unresolved and appeared at δ, 8.59

ppm (Table 2.23). In complex 19, these signals were resolved and appeared as a set of

two peaks at δ, 7.9 (H4) and 7.3 (H

6) ppm. The H

5 signal of free ligand appeared at δ,

7.10 ppm which also moved upfield in this complex at δ, 6.1 ppm. Similar complexes, 20

- 23, showed upfield shifts of signals in the ranges, δ, 7.3 - 8.43 ppm (H

4, H

6) and δ, 6.1

- 6.4 ppm (H5). The o-, m- and p- hydrogens of PPh3 and other P-Ph moieties

(diphosphines), appeared as mutliplets in the ranges; 7.42 - 7.86 (o-H); 7.26 - 7.77 (m-H)

and 7.03 - 7.33 (p-H).

31

P NMR spectral studies

Complex 19 showed one 31

P NMR signal, at δ, 19.4 ppm showing bonding of P donor

atom to metal. Similarly, each of complexes 20, 22, 23 showed only one signal. (Table

2.24). But complex 21 showed two signals at δ, 34.6, 30.46 ppm. The two peaks in

complexes are probably due to the equilibrium between coordinating and non

coordinating pyrimidine - 2 - thiolates (VIII, VIIIa).

95

Ru

S

S

N

NP

P

Ru

S

S

N

NP

P

VIII VIIIa

Table 2.23: 1H NMR spectra (δ, ppm) of complexes 19 – 23.

Complex H4, H

6 H

5

pymSH 8.59 7.10

[Ru(η2-N

1, S-pymS)2(PPh3)2] 19

7.90, 7.30 6.10

[Ru(η2-N

1,S- pymS)2(dppm)] 20

8.43, 8.20 6.64

[Ru(η2-N

1,S-pymS)2(dppe)] 21

8.20, 8.10 6.63

[Ru(η2-N

1,S- pymS)2(dppp)] 22

7.90, 7.90 6.10

[Ru(η2-N

1,S- pymS)2(dppb)] 23

7.95, 7.60 6.10

N

N S1

2

34

5

6

H

HH

H

Table 2.24: 31

P NMR spectra (δ, ppm)of complexes 19 – 23.


[Ru(η2-N

1,S- pymS)2(PPh3)2] 19

19.4 24.1

[Ru(η2-N

1, S- pymS)2(dppm)] 20

9.7 14.4

[Ru(η2-N

1, S- pymS)2(dppe)] 21

34.6, 30.5 39.3, 35.2

[Ru(η2-N

1, S- pymS)2(dppp)] 22

42.0 46.7

[Ru(η2-N

1, S- pymS)2(dppb)] 23

48.8 53.5

96

13C - NMR spectral studies

The 13

C NMR spectra of ruthenium (II) complexes (19 - 23) is shown in Table 2.25.

These data clearly supported coordination through N and S atoms to Ru. The C2 signal

appeared at low field in the range, δ, 181.5 - 188.1 ppm. The signals due to C4 and C

6 are

resolved and appear at high field. The signal due to C5 appeared as a single peak at high

field in the range, δ, 113.1 - 118.2 ppm. The P-Ph moieties showed signals in the range, δ

128.4 - 133.9 ppm. The CH2 signals appear as single or double peaks at, δ 29.7 - 45.71

ppm.

Complex C2 C

4, C

6 C

5 P-Ph moieties

pymSH [154] 181.4 158.6,

154.6

119.1

[Ru(η2-N

1,S- pymS)2(PPh3)2] 19

188.1 155.2,

153.4

118.2 128.9-134.2

[Ru(η2-N

1, S- pymS)2(dppm)] 20

184 156.1,

155.1

_ 128.0 -131.9

[Ru(η2-N

1, S- pymS)2(dppe)] 21

_ 155.1,

155.8

114.2 128.0 – 134.0

[Ru(η2-N

1, S- pymS)2(dppp)] 22

181.3 154.9,

153.9

115.2 127.5-132.2

[Ru(η2-N

1, S- pymS)2(dppb)] 23

188.3 155.0,

154.0

113.1 127.4-133.0

N

N S1

2

34

5

6

H

HH

H

97

Copper (I) Complexes

Pyrimidine-2-Thione Complexes

Synthesis

To copper(I) chloride dissolved in dry acetonotrile was added solid pyrimidine - 2 -

thione (pymSH), followed by the addition of triphenylphosphine (PPh3) in 1 : 1 : 1 molar

ratio for preparing a dimeric complex, [Cu2Cl2(µ-S-pymSH)2(PPh3)2]. However, the

analytical data has supported the formation of a mononuclear complex, [CuCl(η1-S-

pymSH)(PPh3)2] 24. Similar was behaviour with copper(I) bromide, resulting in the

formation of [CuBr(η1-S-pymSH)(PPh3)2] 25. Complexes 24 and 25 were also prepared

by 1 : 1 : 2 (Cu : pymSH : PPh3) molar ratio. Copper(I) iodide neither formed a dimer of

the type, [Cu2I2(µ-S-pymSH)2(PPh3)2], nor a mononuclear complex, [CuI(η1-S-

pymSH)(PPh3)2]. Rather it formed a dimer, [Cu2(μ-I)2(PPh3)2(μ-N3,S-pymSH)].CH3CN,

26 with unusal bonding mode by pyrimidine - 2 - thione. These complexes are soluble in

dichloromethane, chloroform and acetone.

2CuX + 2N

N S

H

+ 2PPh3

Cu

X

PPh3

PPh3

HN S

X = Cl,24; Br,25

[Cu2X2 ( -S-pymSH)2(PPh3)2]

98

When copper(I) iodide was reacted with pyrimidine - 2 - thione in the presence of tri-

tolylphosphines, it formed neither mononuclear complexes nor dinuclear complexes.

Surprisingly, pyrimidine - 2 - thione did not bind to Cu1 center in presence of these

substituted phosphines. Instead tri-o-tolylphosphine formed a dimer Cu2(µ-I)2(o-tol3P)2,

tri-p-tolylphosphine formed a cubane Cu4I4(p-tol3P)4 [197] and tri-m-tolyl formed

adamantane, 30. Direct reactions of CuI with tri-tolyl phosphines in 1: 1 molar ratios also

gave the same products.

CuI + pymSH + o-tol3P

CH3CN

CHCl3

Cu2I2( -S-pymSH)2(o-tol3P)2

CuI( 1-S-pymSH)(o-tol3P)

Cu2(µ-I)2(o-tol3P)2

Cu Cu

I

I

Ph3P PPh3

N S

26

2CuI + 2N

N S

H

+ 2PPh3 [Cu2I2 ( -S-pymSH)2(PPh3)2]

S N =N

NH

S

3

99

CuI + pymSH + m-tol3P

CH3CN

CHCl3

Cu2I2( -S-pymSH)2(m-tol3P)2

CuI( 1-S-pymSH)(m-tol3P)2

[Cu6( 2-I)( 3-I)4( 4-I)(m-tolyl3P)4(CH3CN)2] 30

CuI + pymSH + p-tol3P

Cu4I4(p-tol3P)4

CH3CN

CHCl3

Cu2I2( -S-pymSH)2(p-tol3P)2

CuI( 1-S-pymSH)(p-tol3P)2

Purine-6-thione complexes

To copper(I) chloride dissolved in acetonitrile was added purine - 6 - thione

(puSH2), red precipitates were formed. These precipitates were suspended in methanol

and addition of 2 moles of triphenylphosphine (PPh3) gave crystals of stoichiometry,

[Cu(η2-N

7,S-puSH)(PPh3)2]∙CH3OH 27. When the crystals were left in the air, solvent

molecules evaporate and thus these crystals become opaque. With one mole of PPh3, no

crystalline product could be formed and the contents remained turbid. Complexes,

[Cu(η2-N

7,S-puSH)(PPh3)2]∙CH3OH, 28, and [CuI(η

1-S-puSH2)(PPh3)2], 29, were formed

using copper(I) bromide/iodide respectively. 27 and 28 have same structure but differ in

packing interactions (vide infra). The iodide remained bonded to CuI metal center, unlike

chloride or bromide which got detached as HCl or HBr.

CuX +N

N

N

N

SH

H

2PPh3

Cu

N

PPh3

PPh3

S

27, 28

- HX(X=Cl, Br)

N

N

N

N

S-

S N =

H

100

N

N

N

N

SH

H

CuI+Cu

I

PPh3

PPh3

HN S

29

2PPh3S NH

=N

N

N

N

SH

H

These complexes are not soluble in dichloromethane, chloroform and acetone but are

soluble in dimethylsulphoxide.

Infrared spectroscopy

The IR spectrum of free pyrimidine - 2 - thione showed a characteristic broad

peak at 3400 cm-1

due to ν(N – H) (Table 2.26). In complex 24, it appeared at 3460 cm-1

which showed that there is no deprotonation of pyrimidine - 2 - thione. This peak

appeared in the range of 3460 - 3480 cm-1

in complexes 25 and 26. The ν(C = S) peak of

free ligand pymSH at 980 cm-1

appeared in the low energy region 790 - 850 cm-1

in

complexes 24 - 26. The presence of characteristic ν(P – C) peaks in complexes 24 – 26,

at 1090 - 1190 cm-1

revealed coordinated phosphines in all the complexes. The peaks due

to ν(C – N), ν(C – C) and δ(N – H) lie in the region, 1415 - 1600 cm-1

.

The IR spectrum of free purine - 6 - thione showed a characteristic broad peak at

3431 cm-1

due to ν(N – H) (Table 2.26). In complexes 27 - 29, it appeared in the region,

3382 - 3440 cm-1

. In these complexes, the ν(C = S) peaks, again showed low energy

shifts in the range, 790 - 871 cm-1

as compared to free puSH2 ligand (868 cm-1

). The

presence of characteristic ν(P – C) peaks, in the range, 1090 - 1095 cm-1

revealed

coordinated phosphines in complexes 27 – 29. The ν(C – N) peaks remained almost

unshifted in complexes. The shifting of ν(C = S) peaks to low energy region revealed that

the coordination occured mainly through S donor atoms in all these complexes.

101



Complexes (N H)

(C H) (C C) ...

, (C N) ...,

(N H)

(C S) (P C)

pymSH 3400br 2910w 1560m, 1460s, 1480s 980br -

24 3460w 3160w 1570s, 1490s 850s 1090m

25 3480w - 1570m,1470s 820m 1190m

26 3460w 3160w 1580s, 1450m 790m 1180m

puSH2 3431s 3095w 1573m,1471s 868s -

27 3382w 3049w 1596s, 1481s 858w,790s 1093m

28 3440w 3049w 1550s, 1481m 848m 1093m

29 3400w 3049w 1537m,1477s 871w,836s 1093m

30 - 3029s - - -

Structures of Cu(I) complexes


The crystal structures of [CuCl(η1-S-pymSH)(PPh3)2], 24, [CuBr(η

1-S-

pymSH)(PPh3)2], 25 and [Cu2(μ-I)2(PPh3)2(μ-N3,S-pymSH)]∙CH3CN, 26 are described in

this section [131-133]. Complexes 24 – 26 crystallised in monoclinic crystal system.

(Table 2.27 – 2.29).

In complex [CuCl(η1-S-pymSH)(PPh3)2], 24, Cu

I is coordinated to one S atom

one Cl atom and two P atoms of two triphenylphosphine ligands (Figure 2.19). The

angles around Cu lie in the range, 98.092(16) - 122.00(18)º, which reveal distorted

tetrahedral geometry (Table 2.33). The Cu – S bond distance, 2.3720(7) Å, in the

complex is comparable to 2.356(1) Å, in dimeric complex, [Cu2Cl2(µ-S-pymSH)2(p-

tol3P)2] [137], but slightly longer than the bond distance, 2.2805(5) Å, in mononuclear

complex, [CuCl(η1-S pymSH)(dppp)] (dppp = Ph2P(CH2)3PPh2) [135] and 2.206(2) Å, in

[Cu(pymSH4)2Cl] [129]. The Cu – Cl bond distance, 2.3674(7) Å. is slightly longer

than, 2.300(1) Å, in [Cu2Cl2(µ-S-pymSH)2(p-tol3P)2] [137] and 2.317(3) Å in

102

[Cu(pymSH4)2Cl] [129], but it is shorter than, 2.4071(5) Å, observed in [CuCl(η1-S-

pymSH)(dppp)] [135]. The Cu – P(1) bond distances, 2.2805(5), 2.2899(8) Å. are

comparable to, 2.2698 (1) Å, observed in [CuCl(η1-S-pymSH)(dppp)] [135].

Figure 2.19. Molecular structure of [CuCl(η1-S-pymSH)(PPh3)2] 24 with numbering

scheme.

The packing diagram of 24, shows the presence of both intra- as well as inter-

molecular interactions (Figure 2.20). The intra-molecular interaction is between chlorine

atom and hydrogen atom of the nitrogen, {NH∙∙∙Cl, 2.143 Å} (N∙∙∙Cl, 3.407 Å) (sum of

van der Waals radii of H and Cl atoms, 2.90 Å [195]). The intermolecular contact is

between the Cl atom in one molecule and H atom of phenyl ring in the adjacent molecule

{CH∙∙∙Cl, 2.748 Å}(C∙∙∙Cl, 3.566 Å; C-H∙∙∙Cl angle, 148.04°). This generates 1D

polymer. The Cl atoms of one 1D polymer interact with the hydrogen atoms of the

phenyl ring of another 1D polymer and formed a 2D network {CHphenyl∙∙∙Cl, 2.905

Å}(C∙∙∙Cl, 3.687 Å; C-H∙∙∙Cl angle, 129.65°).

103

Figure 2.20. Packing diagram of [CuCl(η1-S-pymSH)(PPh3)2] 24.

In complex [CuBr(η1-S-pymSH)(PPh3)2], 25, Cu

I is coordinated to one S atom of

pymSH, one Br atom and two P atoms of two triphenylphosphine ligands. The different

orientation of coordinated atoms around Cu generate crystallographically independent

molecules in the lattice (Figure 2.21). The angles around Cu lie in the range, 99.72(2) -

124.97(3)º (Table 2.33). The Cu – S bond distance, 2.3530(11) Å, is longer than,

2.2903(4) Å, observed in [CuBr(η1-S-pymSH)(dppp)] [135], but comparable to 2.389

(19) Å, as observed in [Cu2Br2(µ-S-pySH)2(PPh3)2] (pyridine-2-thione) [54]. The Cu –

Br bond distance, 2.5173(8) Å, is comparable to 2.5369 Å found in [CuBr(η1-S-

pymSH)(dppp)] [135], and slightly longer than, 2.4455(11) Å, observed in [Cu2Br2(µ-S-

pySH)2(PPh3)2] [54]. The Cu – P(1) bond distances, 2.2628(9), 2.2982(10) Å are

comparable to 2.2688 Å , 2.2715 (7) Å observed in [CuBr(η1-S-pymSH)(dppp)] [135],

but are slightly longer, 2.2376(13) Å, than in [Cu2Br2(µ-S-pySH)2(PPh3)2] [54].

104

Figure 2.21. Molecular structure of [CuBr(η1-S-pymSH)(PPh3)2] 25 with numbering

scheme. Two independent molecules with same unit.

Complex [Cu2(μ-I)2(PPh3)2(μ-N3,S-pymSH)].CH3CN, 26 has bridging through

iodide having Cu(-I)2Cu core. Each Cu is also bridged through N, S donor atoms of

neutral pyrimidine - 2 - thione, and is further bonded to a P atom of triphenylphosphine

(Figure 2.22). One acetonitrile molecule is also lying in the crystal lattice. The Cu∙∙∙Cu

separation of 2.675(2) Å is less than the sum of van der Waals radius of Cu atoms, 2.80

Å, and it is the shortest Cu∙∙∙Cu contact among copper(I)-heterocyclic thioamide dimers,

known so far [52, 57, 58,141]. The geometry around each Cu center {CuI2PN; CuI2PS

cores) is distorted tetrahedral with angles varying in the range, 102 - 119o (Table 2.33).

The Cu(2) – I(1) – Cu(1) and Cu(2) – I(2) – Cu(1) bond angles are acute {59.94(4)o,

59.52(4)o}, while the angles P(1) – Cu(2) – I(1) and P(2) – Cu(1) – I(2) {106.53(8)

o,

118.76(9)o} are obtuse.

The Cu – I distances are 2.7043(14) Å, 2.6655(14) Å (Table 2.33), that can be

comparable to 2.674(2) Å of [CuI(η1-S-pymSH)(PPh3)2] [133]. This distance is longer

105

than the Cu – Cl distance, 2.300 Å in the dimer, [Cu2Cl2(µ-S-pymSH)2(p-tol3P)2] [137].

The Cu – P distances are, 2.233(3) Å and 2.2303(3) Å, which are shorter than {2.296(4)

Å, 2.303(4) Å} in case of [CuI(η1-S-pymSH)(PPh3)2] [133]. The Cu – S distance is

2.304(3) Å, which is almost same as in [CuI(η1-S-pymSH)(PPh3)2] {2.338 (4) Å} [133].

This is the first example of such type of -N,S- bridging in case of dimers of heterocyclic

thioamides [1-4].

Figure 2.22. Molecular structure of [Cu2(μ-I)2(PPh3)2(μ-N3,S-pymSH)]∙CH3CN 26 with

numbering scheme.

In the packing of complex 26, the bridged iodine in one molecule interacts with the H

atom of the pyrimidyl ring {CH∙∙∙I, 2.976 Å} (I∙∙∙C, 3.720 Å; C-H∙∙∙I angle, 133.45°)

106

(Figure 2.23) (sum of van der Waal radii of I and H atoms, 3.150 Å [195]). This

interaction makes it a 1D polymer. The two 1D chains are also interacting through similar

interaction between two chains as bridged iodine in one 1D chain interact with H atoms

of phenyl rings of second 1D chain, {CHphenyl∙∙∙I, 3.144 Å}(C∙∙∙I, 3.965 Å; C-H∙∙∙I angle,

148.39°) (sum of van der Waal radii of I and H atoms, 3.150 Å [195]). This generates a

2D network of the complex with cavities occupied by acetonitrile molecules. Acetonitrile

interacts with NH hydrogen atom of the pyrimidyl ring, {NH∙∙∙NCH3CN, 2.238 Å} (N∙∙∙N,

2.897 Å; C-H∙∙∙C angle, 154.22°) (sum of van der Waal radii of N and H atoms, 2.75 Å

[195]).

Figure 2.23. Packing diagram of Cu2(μ-I)2(PPh3)2(μ-N3,S-pymSH)]∙CH3CN 26.

107

Purine-6-thione Complexes

The crystal structures of [Cu(η2-N

7,S-puSH)(PPh3)2]∙CH3OH 27, [Cu(η

2-N

7,S-

puSH)(PPh3)2]∙CH3OH 28 and [CuI(η1-S-puSH2)(PPh3)2] 29 are described in this

section. Complexes 27, 28 and 29 crystallized in monoclinic crystal system. (Tables 2.31

– 2.33).

In complex [Cu(η2-N

7,S-puSH)(PPh3)2]∙CH3OH 27, copper is coordinated to

nitrogen (N7) and sulphur atoms of puSH

-, and two P atoms of two triphenylphosphine

ligands (Figure 2.24). The N4 atom of the thio-ligand makes hydrogen bond with oxygen

atom of methanol. The angles around copper atom lie in the range, 88.61(5)°-

126.51(19)°, and reveal that geometry around copper is severely distorted tetrahedral

(Table 2.34). The Cu – S bond distance, 2.4312(5) Å, is slightly longer than, 2.3720(7) Å,

observed in complex 24, and 2.356(1) Å in [Cu2Cl2(µ-S-pymSH)2(p-tol3P)2] [137]. The

Cu – P bond distances, 2.2547(5), 2.2663(5) Å, are comparable with similar Cu – P

distances, 2.2805(5), 2.2899(8) Å found in complex 24. The Cu – N bond distance is

2.1230(16) Å, which is longer than 2.090(8) Å in complex 26. In this complex, the Cu –

Cl bond gets ruptured, leading to the chelation of purine-6-thione. The methanol

molecule present in it makes H-bond with N4 atom of the thio-ligand. This rupture of Cu

– Cl bond is further stabilized by H-bond.

The packing diagram shows the methanol molecule plays a very important role in

stabilizing the crystal lattice (Figure 2.25). Two complex molecules are linked through

two methanol molecules via MeOH∙∙∙N {1.941 Å}(N∙∙∙O, 2.772 Å; N-H∙∙∙O angle,

170.17°) and OMeOH∙∙∙HCphenyl {2.708 Å} interactions (sum of van der Waal radii of O

and H atoms, 2.70 Å and N and H atoms, 2.75 Å [195]). This process generates a 1D

zig-zag chain polymer. The phenyl hydrogen atoms of one 1D chain interact with the

nitrogen atoms of purine rings of the second 1D chain {CHphenyl∙∙∙N, 2.607 Å}(N∙∙∙C,

3.383 Å; C-H∙∙∙N angle, 130.11°) (sum of van der Waal radii of N and H atoms, 2.75 Å

[195]). This interaction between 1D chains forms a 2D sheet.

108

Figure 2.24. Molecular structure of [Cu(η2-N

7,S-puSH)(PPh3)2]∙CH3OH 27 with

numbering scheme.

Figure 2.25. Packing diagram of [Cu(η2-N

7,S-puSH)(PPh3)2]∙CH3OH 27.

109

In complex [Cu(η2-N

7,S-puSH)(PPh3)2]∙CH3OH 28, copper is coordinated to

nitrogen and sulphur atom of puSH-, and two P atoms of two triphenylphosphine ligands

(Figure 2.26). The methanol molecule is also present in crystal lattice and it makes H-

bond with N2H atom of the ligand. The stiochiometry of this complex is the same as

complex 27 and the bond parameters are almost similar (Table 2.34). But the packing

diagram of this complex, is somewhat different from that of 27 and is described below.

Figure 2.26. Molecular structure of [Cu(η2-N

7,S-puSH)(PPh3)2]∙CH3OH 28 with

numbering scheme.

The packing diagram shows that the methanol molecule again plays an important

role in stabilizing the crystal lattice (Figure 2.27). The oxygen atom of methanol

connects two complex molecules via MeOH∙∙∙N, {2.000 Å}(N∙∙∙O, 2.807 Å; O-H∙∙∙N

angle, 167.74°) and NHpyrimidyl∙∙∙OMeOH, {1.955 Å}(N∙∙∙O, 2.809 Å; N-H∙∙∙O angle,

171.12°) interactions (sum of van der Waal radii of N and H, 2.75 Å and O and H,

110

2.70 Å [195]). Two complex molecules also show CH∙∙∙π interactions {2.744 Å}

(C∙∙∙C, 3.559 Å; C-H∙∙∙C angle, 146.81°) between phenyl rings. This generates a 1D

polymer. Two 1D polymers show interaction between N atom of six membered ring

in purine-6-thione in 1D chain with H atom of the phenyl ring in another 1D chain

{CHphenyl∙∙∙N, 2.658 Å}(C∙∙∙N, 3.399 Å; C-H∙∙∙N angle, 137.23°) (sum of van der

Waal radii of N and H atoms, 2.75 Å, [195]) and form 2D sheets.

Figure 2.27. Packing diagram of [Cu(η2-N

7,S-puSH)(PPh3)2]∙CH3OH 28.

The rupture of Cu – X (X = Cl, Br, I) bonds is not common in CuX - heterocyclic

thioamide chemistry [52-57, 128-146]. The basic difference in these complexes is the

hydrogen bonding of methanol molecule with the purine - 6 - thione rings. In complex

27, the hydrogen bond is between N4 nitrogen atom with the H atom of the methanol, but

in complex 28, the hydrogen bond is between N2H atom with the O atom of the

111

methanol. Due to this difference packing diagram of complex 28 is different from that of

27.

In complex [CuI(η1-S-puSH2)(PPh3)2] 29, Cu is coordinated to one S atom of

puSH2, one iodine atom and two P atoms of two triphenylphosphine ligands forming a

monomer (Figure 2.28). The angles aroud Cu, 101.321(18) – 121.761(19)°, reveal a

distorted tetrahedral structure. The Cu – S bond distance, 2.3574(5) Å, is comparable to,

2.3530(11) Å, in complex 25 (Table 2.34). The Cu – P bond distances, 2.2788(5),

2.2750(9) Å are shorter than, 2.2805(5), 2.2899(8) Å observed in complex 24. The Cu – I

bond distance, 2.6842(3) Å, is comparable, to that {2.7010(4) Å} in complex 26.

Copper(I) iodide with purine-6-thione makes a S - bonded monomer unlike CuCl or CuBr

where N, S-chelation by uninegative puSH- ligand takes place.

Figure 2.28. Molecular structure of [CuI(η1-S-puSH2)(PPh3)2] 29 with numbering

scheme.

112

In the packing diagram of 29, iodine atom of one complex molecule has

intramolcular interaction with hydrogen atom at N of the same molecule {3.433 Å} (sum

of van der Waal radii of I and H, 3.50 Å [195]) (Figure 2.29). The N atom of five

membered ring in purine-6-thione interacts with H atom of the phenyl ring of second

molecule, NH∙∙∙I, 2.856 Å (N∙∙∙I, 3.391 Å; C-H∙∙∙C angle, 134.56°). Again the C - H

hydrogen of five membered ring interacts with the iodine atom of the second molecule,

CH∙∙∙I, 3.081 Å (C∙∙∙I, 3.883 Å; C-H∙∙∙I angles, 143.04°) (sum of van der Waal radii of I

and H, 3.15 Å [195]). This generates a 1D polymer. Two 1D chains are interacting

through NH∙∙∙N interaction of opposite purine-6-thione rings with bond contacts of 2.058

Å (N∙∙∙N, 2.899 Å; N-H∙∙∙N angle, 162.91°) (sum of van der Waal radii of N and H, 2.75

Å [195]). There is also an additional contact between iodine atom in one 1D chain with H

atom of six membered ring of purine-6-thione of another 1D chain with CH∙∙∙I, contact of

3.018 Å (C∙∙∙I, 3.883 Å; C-H∙∙∙I angle, 151.21°) (sum of van der Waal radii of I and H,

3.15 Å [195]). This generates a 2D sheet polymer.

Figure 2.29. Packing diagram of [CuI(η1-S-puSH2)(PPh3)2] 29

113

As described earlier, copper(I) iodide with pyrimidine-2-thione in the presence of tri-

o-tolylphosphine, formed a dimer, [(o-tolyl3P)Cu(µ-I)2Cu(o-tolyl3P)] [198]. Similarly, tri-

p-tolylphosphine formed a cubane, [Cu4I4(p-tolyl3P)4] [198]. The tri-m-tolylphosphine

formed adamantane whose structure is described below. The structure of adamantane

[Cu6(2-I)(3-I)4(4-I)(m-tolyl3P)4(CH3CN)2] 30, is shown in Figure 2.30. In this

complex, four Cu atoms are coordinated to four terminally bonded m-tolyl3P ligands, two

Cu atoms are bonded to two CH3CN ligands and iodide ligands have 2-I, 3-I and 4-I,

bonding modes. This compound has four CuI3P and two CuI3N cores, and geometry

around each Cu center is distorted tetrahedral. The polarisable iodide ligand and the

position of methyl group in phenyl ring attached to P atom appear to have played the

pivotal role in the construction of monomeric bicapped adamantoid geometry, which is

unique and unprecedented in copper chemistry. Figure 2.31 shows the bicapped

adamantoid cluster with m-tolylphosphine and methyl groups only.

Figure 2.30. Molecular structure of [Cu6(2-I)(3-I)4(4-I)(m-tolyl3P)4(CH3CN)2] 30

with numbering scheme.

114

Figure 2.31. Structure of bicapped admanatnoid cluster 30 with m-tolyl and CH3

groups

In conclusion, while pyrimidine - 2 - thione with copper(I) chloride/bromide formed

usual tetrahedral complexes, [CuX(pymSH)(PPh3)2], the purine - 6 - thione rather

formed, [Cu(puSH)(PPh3)2] with no CuI-halogen bonds. Similarly, copper(I) iodide with

pymSH in presence of triphenylphosphine formed unusual dimer [Cu2(μ-I)2(PPh3)2(μ-

N3,S-pymSH)]. Purine - 6 - thione, on the other hand, formed usual tetrahedral complex,

[CuI(puSH2)(PPh3)2].

115

Table 2.27: Crystal data for [CuCl(η1-S-pymSH)(PPh3)2] 24

Empirical formula C40H34ClCuN2P2S


(Å) 0.71073 Å


Space group P21/c


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

14.340(4) Å

10.111(3)Å

24.200(5) Å

90.00

94.363(7)º

90.00

Volume (Å3) 3498.6(15)

Z 4

Density calcd. (g/m3). 1.397

F(000) 1520

Crystal description Orange block


) 0.884

T (K) 150(2)

2θ range (º) 2.28 – 27.62

Index ranges -18 h 18, -13 h 13

-30 h 31



Max./min.transmission 0.6484, 0.8664

Refined parameters 428


R, Rw 0.0277, 0.0750

Peak and hole ( e Å-3

) -0.348, 0.421

116

Table 2.28: Crystal data for [CuBr(η1-S-pymSH)(PPh3)2] 25

Empirical formula C40H34BrCuN2P2S


(Å) 0.71073


Space group P21/n


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

12.825(4) Å

43.122(15) Å

13.396(5) Å

90.00

90.792(6)º

90.00

Volume (Å3) 7408(4)

Z 8

Density calcd.. (g m-3

). 1.399


) 1.842

F(000) 3184

Crystal description Orange rod

2θ range (º) 56.04

Index ranges -16 h 16, -56 h 56

-18 h 18



Max./min.transmission 0.677, 1.000

Refined parameters 855


R, Rw 0.0383, 0.0777


) -0.360, 0.457

117

Table 2.29: Crystal data for [Cu2(μ-I)2(PPh3)2(μ-N3,S-

pymSH)]∙CH3CN 26

Empirical formula C42H37Cu2I2N3P2S


(Å) 0.71073


Space group P2(1) (No. 2)


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

9.896

18.378

11.703

90

101.73

90

Volume (Å3) 2084.0

Z 2



) 2.662

F(000) 1040

Crystal description Orange prismatic

2θ range (º) for data collection 3.02 - 28.02

Index ranges -13 h 1,- 24 k

24, -15 l 15



Data parameters 469


R, Rw 0.0586, 0.1007


) 0.737, -1.042

118

Table 2.30: Crystal data for [Cu(η2-N

7,S-puSH)(PPh3)2]∙CH3OH

27

Empirical formula C41H33CuN4P2S.CH4O

Formula weight(M) 771.30

Wavelength(Å) 0.71073



Space group P121/n1


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

9.0449(3)

25.0605(7)

16.8117(5)

90

102.404(3)

90

Volume (Å3) 3721.75(19)

Z 4


Crystal shape/ colour Chunk/ Colorless


) 0.768

F(000) 1600

Crystal size (mm3) 0.44 0.37 0.31


Index range -13 h 12, -36 k 37, -

24 l 19



R, Rw

0.0440, 0.0769

119

Table 2.31: Crystal data for [Cu(η2-N

7,S-puSH)(PPh3)2]∙CH3OH

28

Empirical formula C41H33CuN4P2S.CH4O

Formula weight(M) 771.30

Wavelength(Å) 1.54184



Space group P121/n1


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

9.1063(5)

25.229(2)

16.9667(19)

90

102.115(8)

90

Volume (Å3) 3811.2(6)

Z 4


Crystal shape/ colour Prism/ Colorless


) 2.413

F(000) 1600

Crystal size (mm3) 0.44 0.32 0.16


Index range -11 h 11, -29 k 31,

-21 l 21



R, Rw

0.08, 0.16

120

Table 2.32: Crystal data for [CuI(η1-S-puSH2)(PPh3)2] 29

Empirical formula C41H34CuIN4P2S





Space group P21/n


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

11.2972(5)

14.6354(7)

22.5112(10)

90

98.9310(10)

90

Volume (Å3) 3676.9(3)

Z 4


Crystal shape/ colour Block/ yellow


) 1.614

F(000) 1744

Crystal size (mm3) 0.49 0.40 0.24


Index range -11 h 14, -18 k 19,

-30 l 29


Unique reflections, Rint 8989 , 0.0222


R, Rw

0.0305, 0.0737


) 1.435 and -0.279

121

Table 2.33: Crystal data for [Cu6(2-I)(3-I)4(4-I)(m-

tolyl3P)4(CH3CN)2] 30

Empirical formula C88H84P4Cu6I6N2


(Å) 0.71073

Crystal system Cubic

Space group Fd-3 (#203)


a (Å)

b (Å)

c (Å)

α (º)

β (º)

γ (º)

26.3990(7)

Volume (Å3) 18397.7(8)

Z 8

Crystal Color, Habit Colorless, Prism

Crystal Dimensions (mm) 0.15 X 0.20 X 0.30



) 34.88

F(000) 5856.00

T (K) -80.0 oC

2θ range(º) for data collection 8.0 - 55.0



R

Rw

0.023

0.067



) 1.67, -0.41

122

Table 2.34: Selected bond lengths (Å) and bond angles (º) of complexes 24 – 27, 29 and

30.

[CuCl(η1-S-pymSH)(PPh3)2] 24

Cu(1) P(1) 2.2805(5) P(1) Cu(1) P(2) 122.00(18)

Cu(1) P(2) 2.2899(8) P(1) Cu(1) S(1) 102.22(2)

Cu(1) Cl(1) 2.3674(7) P(2) Cu(1) S(1) 113.708(18)

Cu(1) S(1) 2.3720(7) P(1) Cu(1) Cl(1) 111.885(17)

S(1) C(1) 1.6914(16) P(2) Cu(1) Cl(1) 98.092(16)

N(1) C(1) 1.360(2) S(1) Cu(1) Cl(1) 108.750(4)

N(2) C(1) 1.362(2) Cu(1) S(1) C(1) 113.43(6)

N(1) C(4) 1.323(2) S(1) C(1) N(1) 120.48(12)

N(2) C(2) 1.348(2) S(1) C(1) N(2) 120.73(11)

[CuBr(η1-S-pymSH)(PPh3)2] 25

Cu(1) P(1) 2.2628(9) P(1) Cu(1) P(2) 124.97(3)

Cu(1) P(2) 2.2982(10) P(1) Cu(1) S(1) 106.779(3)

Cu(1) Br(1) 2.5173(8) P(2) Cu(1) S(1) 105.94(3)

Cu(1) S(1) 2.3530(11) P(1) Cu(1) Br(1) 107.49(3)

S(1) C(1) 1.691(3) P(2) Cu(1) Br(1) 99.74(2)

N(1) C(1) 1.362(3) S(1) Cu(1) Br(1) 111.69(2)

N(2) C(1) 1.352(3) Cu(1) S(1) C(1) 108.25(10)

N(1) C(2) 1.343(3) S(1) C(1) N(1) 120.5(2)

N(2) C(4) 1.323(4) S(1) C(1) N(2) 121.1(2)

123

[Cu2(μ-I)2(PPh3)2(μ-N3,S-pymSH)].CH3CN 26

Cu(2) P(1) 2.233(3) P(2) Cu(1) S(1) 111.77(11)

Cu(1) P(2) 2.230(3) P(2) Cu(1) Cu(2) 158.18(10)

Cu(1) I(2) 2.7010(14) S(1) Cu(1) Cu(2) 88.86(8)

Cu(1) S(1) 2.304(3) P(2) Cu(1) I(2) 118.76(9)

Cu(2) N(2) 2.090(8) S(1) Cu(1) I(2) 102.81(9)

Cu(2) I(1) 2.6459(14) Cu(2) Cu(1) I(2) 59.98(4)

Cu(1) I(1) 2.7076(14) P(2) Cu(1) I(1) 106.10(8)

Cu(2) I(2) 2.6872(14) S(1) Cu(1) I(1) 107.25(9)

Cu(1) Cu(2) 2.6747(17) Cu(2) Cu(1) I(1) 58.89(4)

P(1) Cu(2) I(2) 108.77(9) N(2) Cu(2) P(1) 116.1(2)

Cu(2) I(1) Cu(1) 59.94(4) P(1) Cu(2) I(1) 106.53(8)

N(2) Cu(2) I(1) 105.2(2) N(2) Cu(2) I(2) 108.2(2)

[Cu(η2-N


Cu-N(1) 2.1230(16) N(1)-Cu-P(1) 107.84(5)

Cu-P(1) 2.2547(5) N(1)-Cu-P(2) 108.44(5)

Cu-P(2) 2.2663(5) P(2)-Cu-P(1) 126.502(19)

Cu-S(1) 2.4312(3) N(1)-Cu-S(1) 88.67(5)

P(2)-Cu-S(1) 101.529(19) P(1)-Cu-S(1) 117.26(2)

[Cu(η2-N


Cu-N(1) 2.130(4) N(1)-Cu-P(1) 108.63(11)

Cu-P(1) 2.275(11) N(1)-Cu-P(2) 108.13(10)

Cu-P(2) 2.263(11) P(2)-Cu-P(1) 125.80(4)

Cu-S 2.438(12) N(1)-Cu-S 88.20(10)

P(2)-Cu-S 117.80(4) P(1)-Cu-S 101.77(4)

124

[CuI(η1-S-puSH2)(PPh3)2] 29

Cu(2)-P(2) 2.2750(5) P(2)-Cu(2)-P(1) 121.761(19)

Cu(2)-P(1) 2.2788(5) P(2)-Cu(2)-S(5) 101.321(18)

Cu(2)-S(5) 2.3574(5) P(1)-Cu(2)-S(5) 107.999(18)

Cu(2)-I(1) 2.6842(3) S(5)-Cu(2)-I(1) 108.719(14)

P(2)-Cu(2)-I(1) 112.338(15) C(38)-N(1)-C(37) 125.63(16)

P(1)-Cu(2)-I(1) 104.207(14) C(37)-S(5)-Cu(2) 112.63(7)

C(1)-P(1)-Cu(2) 107.73(6)

[Cu6(2-I)(3-I)4(4- I)(m-tolyl3P)4(CH3CN)2] 30

I(1) Cu(1) 2.6896(6) Cu(1) I(1)Cu(1)1) 110.60(3)

I(1) Cu(1)1) 2.6896(6) Cu(1) I(1) Cu(2) 67.33(3)

I(1)Cu(2) 2.584(1) Cu(1) I(1) Cu(2)1) 67.33(3)

I(1)Cu(2)1) 2.584(1) Cu(1)1) I(1) Cu(2) 67.33(3)

Cu(1) P(1) 2.257(1) Cu(1)1) I(1)Cu(2)1) 67.33(3)

Cu(2)N(1) 2.077(5) Cu(2) I(1) Cu(2)1) 94.76(5)

P(1)C(1) 1.819(4) I(1) Cu(1) I(1)2) 108.90(2)

P(1) C(1)2) 1.819(4) I(1) Cu(1)I(1)3) 108.90(2)

P(1)C(1)3) 1.819(4) I(1)Cu(1)P(1) 110.04(3)

N(1)C(8) 1.05(2) I(1)2) Cu(1) P(1) 110.04(3)

N(1)C(8)4) 1.57(2) I(1)Cu(2)I(1)2) 115.72(4)

C(1C(2) 1.381(6) I(1)Cu(2) N(1) 102.1(2)

I(1)2) Cu(2) I(1)4) 115.72(4) I(1)2) Cu(2) N(1) 102.1(2)

I(1)Cu(2) I(1)4) 115.72(4) I(1)2) Cu(1) I(1)3) 108.90(2)

I(1)4)Cu(2)N(1) 102.1(2) I(1)3) Cu(1) P(1) 110.04(3)

125

NMR Spectroscopy

NMR spectral studies (1H,

13C and

31P NMR) of pyrimidine - 2 - thione/purine - 6

- thione complexes 24 - 29 are described in this section.



The H4, H

6 protons of free ligand, pymSH, were unresolved and appeared at δ,

8.59 ppm (Table 2.34). In complexes 24 - 26, these signals are resolved and appeared as a

set of two peaks, which lie in the ranges, δ, 7.43 - 7.48 (H6), 7.9 - 8.25 ppm (H

4). The H

5

signal of free ligand, pymSH, appeared at δ, 7.10 ppm. But in complexes 24 - 26, it also

appeared upfield, in the range, δ, 6.56 – 6.9 ppm. The o-, m- and p- hydrogens of PPh3,

appear as mutliplets in the ranges; 7.45 - 7.57 (o-H); 7.26 – 7.41 (m-H) and 7.2 -7.37 (p-

H). The NH signal could not be identified due to broading effect of quaderpolar N1 atom.

Table 2.34: 1H NMR spectra (δ, ppm) of complexes 24 – 26.

Complexes H4, H

6 H

5

pymSH 8.59 7.10

24 7.90, 7.43 6.60

25 7.97, 7.45 6.56

26 8.25, 7.48 6.9

N

N S1

2

34

5

6

H

HH

H

126


Complexes 24 and 25 showed one 31

P NMR signal each, at δ = -2.9 and -3.6 ppm

respectively (Table 2.35). However complex 26 showed two signals at δ, 29.1, -4.9 ppm.

These two peaks are due to different environments observed by P atoms of PPh3.

Table 2.35: 31

P NMR spectra (δ, ppm) of complexes 24 - 26


24 -2.9 1.8

25 -3.6 1.1

26 29.1, -4.9 33.8, -0.2

13C NMR spectral studies

The 13

C NMR spectral data of complexes, 24 – 26, are given in Table 2.36. The

C2 signal appeared at high field in the range, δ, 180 – 180.5 ppm. The upfield shift of C

2

signals showed coordination of Cu1 to S atom of pymSH. The signal due to C

5 appeared

as a single peak at high field in the range, δ, 109.8 – 109.9 ppm. The P-Ph moieties, lie in

the range, δ 128.14 – 134.08 ppm.

Table 2.36: 13

C NMR spectra (δ, ppm) of complexes 24 - 25

Complex C2 C

4, C

6 C

5 P-Ph moiety

pymSH [154] 181.4 158.6,

154.6

119.1 _

24 180.5 _ 109.9 128.2-134.1

25 180.0 _ 109.8 128.1-134.1

N

N S1

2

34

5

6

H

HH

H

127

Purine -6-thione complexes

NMR spectral studies (1H and

31P NMR) of complexes 27 - 29 are discussed in

this section.

The H2 proton of purine ring shifts downfield in complexes (Table 2.37). The H

8

proton signals showed downfield shifts in complexes 27 and 28, but upfield shift in

complex 29 relative to the free ligands. The phenyl proton signals of phosphine were

multiplets and lie in the broad range, 6.36 – 7.68 ppm.

N

N

N

N

S6 7

8

9

1

23

4

5

H

H

H

H

31

P NMR spectral studies

The 31

P NMR spectral data of purine-6-thione complexes is shown in Table 2.38.

Complex 27 showed one signal while 29 showed two 31

P signals.

Table 2.38: 31

P NMR spectra (δ, ppm) of complexes 27 and 29

Complex Δ Δδ(δcomplex – δligand)

27 27.0 31.7

29 31.8, 0.7 36.5, 5.4

28 is identical to 27.

Table 2.37: 1H NMR spectra (δ, ppm) of complexes

27 – 29

Complex H8 H

2 PPh3

puSH2 7.75 7.10

27 8.11 7.22 7.34-7.68

28 8.14 7.23 7.33-7.68

29 7.25 7.14 6.36-6.82

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