3
Introduction
General
In this thesis, coordination chemistry of CuI, Pd
II, Pt
II and Ru
II metal ions has been
investigated with some heterocyclic thioamides. The interaction of heterocyclic
thioamides with transition, post-transition and main group metals has been the focus of
several investigations [1-10]. These thio-ligands are characterized by thione – thiol
tautomerism and contain chemically active -N(H)-C(=S)- -N(H)-C(=S)-N(H)- type
groups. These adopt thione form in solid state (1a), but adopt thiol form (1b) in solution
phase, particularly in nonpolar solvents [5].
4
6NH
S
2
35
1 N SH
Ia Ib
Most heterocyclic thioamides have one replacable proton and function readily as
monoanions, such as pyridine - 2 - thione (pySH), pyrimidine - 2 - thione (pymSH),
while the disubstituted thiones such as 2- thiouracil (tucH2) and 6 - mercaptopurine
(puSH2) may function as monoanions or dianions. These ligands can bind to metal ions
both as neutral and deprotonated species, via a variety of modes, forming monomers,
dimers, oligomers and polymers.
Pyridine-2-thione, pyrimidine-2-thione, 2- thiouracil and 6 - mercaptopurine are
the thio - analogs of purine and pyrimidine nucleobases, and as such have several
biochemical and other applications. These are used as therapeutic agents,
anticarcinogens, fungicides, polyolefin stabilizers in polymers and plastics, vulcanization
accelerators and inhibitors of metallic corrosion [1-6, 11-29]. Thio - ligands play a major
role in detoxification and sequestration of heavy metals such as Hg [11], S, N- chelation
in Mo complexes is relevant to the reduction of nitrogen by nitrogenase etc. [12]. The
4
gold(I) complexes of thiouracil [13, 14] are used in the treatment of rheumatoid arthritis
and also exhibit carcinostatic activity [15].
Background
Here coordination chemistry of pyridine - 2 - thione (pySH, I) with iron (II),
ruthenium (II), osmium (II), nickel(II), palladium (II), platinum (II), copper(I), silver (I)
and mercury (I) is briefly reviewed [30-62], which provided the background to persue
coordination chemistry of heterocyclic thioamides further.
Fe, Ru, Os
The reaction of FeCl3 with pyridine - 2 - thione followed by its reaction with Ph3P
in ethanol and chloroform gave crystals of [FeCl2(η1 - S - pySH)2] 1 [30] instead of the
expected product [FeCl3(pySH)(Ph3P)2]. In this reaction, reduction of Fe+3
to Fe+2
takes
place. The geometry about Fe(II) is distorted tetrahedral and the ligand is coordinating
through S atom, and the free NH group forms intermolecular hydrogen bond with Cl
atoms of adjacent molecules. In the literature, an ionic complex [pySSpyH]+[FeCl4]
- is
also known [31] .
S
Fe
NH
Cl
1
ClS NH
1
N S
The reaction of Ru(PPh3)3Cl2 with pySH (1:2 ratio) in benzene or toluene in the
presence of triethylamine has formed [Ru(η2-N,S-pyS)2(PPh3)2] 2 [32] complex.
Complex has a distorted octahedral structure. Similar reaction of Ru(dppe)2Cl2 with
pySH in the presence of Et3N in benzene did not form the expected product, [Ru(η2 -
N,S- pyS)2(dppe)] 3 [33], but merely formed crystals of [Ru(dppe)2Cl2] 4 [34]. Thus
complex 3 was prepared by replacing PPh3 from complex 2 by dppe in toluene as a
5
solvent. The compounds with dppm, dppp and dppb, [Ru(η2 - N,S- pyS)2(dppm)], [Ru(η
2
- N,S- pyS)2(dppp)] 5 [35] and [Ru(η2 - N,S- pyS)2(dppb)] 6 [36] were prepared similarly
{dppm = 1,1-bis(diphenylphosphino)methane, dppe = 1,2-bis(diphenylphosphino)ethane,
dppp = 1,3-bis(diphenylphosphino)propane, dppb = 1,4-bis(diphenylphosphino)butane}.
All these complexes have distorted octahedral geometry with trans S atoms (S-Ru-S bond
angles, 154.7 – 155.9°). Similar complexes of Os and pyridine – 2- thione are: [OsII(η
2 -
N,S- pyS)2(PPh3)2] 7 [37], [OsIII
(η2 - N,S- pyS)2(PPh3)2]PF6 8 [37].
2-3, 5-8
N S_
Ru
S
S
N
NP
Ru
S
S
N
NPh3P
Ph3P
2
P
PP = dppe ,3, dppp, 5, dppb, 6
3, 5-6
Ru
P
P
P
P
Cl
Cl
4
+
Os
S
S
N
NPh3P
Ph3P
7
Os
S
S
N
NPh3P
Ph3P
8
Ni, Pd, Pt
Only a few nickel compounds with pyS- namely, [Et4N][Ni(η
2 -N,S- pyS)3] 9
[38], (NBu4)[Ni(C6H5)2(η2 - N,S- pyS)] 10 [39], [Ni(η
1 - S- pyS)2(bipy)]0.5 bipy 11 [40]
and [Ni(pyOS)2] [41] (pyOS = 1-oxo-pyridine-2-thione). Complex 9 has octahedral
geometry while complexes 10 and 11 have square planar geometry.
6
9 -11
N S_
Ni
N
S
10
-S
Ni
SS
N
N
119
N
NN
NiS
-
N
Palladium(II) acetate with pyridine - 2 - thione formed a N, S-bridged dimer,
[Pd2(η2-N,S- pyS)4] 12 [42] and same can be prepared from PdCl2 and Na
+pyS
- in
CH3CN solvent [43]. Platinum(II) has formed similar dimer, [Pt2(η2 -N,S- pyS)4] 13
[44]. Reaction of 13 with PPh3 in 1 : 2 ratio formed square planar [Pt(η1 - S-
pyS)2(PPh3)2] 14 [44] complex. Other tertiary phosphine derivatives structurally
established are: [PdCl(η2-N,S- pyS)(PPh3)] 15 [45] and [Pt(η
2 -N,S- pyS)(PPh3)2]
+(PF6)
-
16 [46].
N
N
M M
SN
SNN
N
S
S
12, 13
N S_
M = Pd, 12; Pt, 13
PPh3
PPh3
Pt
S
N
16
+
PPh3
Ph3P
Pt
S
S
14
12 -16
PPh3
Cl
Pd
S
N
15
7
The use of diphosphines in place of PPh3 also gave different results. Palladium
(II) chloride complex with dppe and pySH in the presence of sodium hydroxide in
ethanol, formed [Pd(η1 - S- pyS)2(dppe)] 17 [47, 48]. Platinum(IV) chloride with pySH
and dppe (or dppen) in the presence of triethylamine in solvent benzene, also yielded
similar complexes, [Pt(η1 - S- pyS)2(L-L)] (L-L = dppe 18, dppen 19) {dppen = 1,2-
bis(diphenylphosphino)ethylene} [47, 48]. These compounds contain chelating
diphosphines and S - bonded pyS groups with pendant pyridyl groups.
N
N
PP = dppe ,17,18, dppen, 19
N S_
P
P
M
S
S
17 - 19
17 - 19
Some other dinuclear complexes reported are: [{Pd(η2 - N,S- pyS)(PMe3)Cl}2] 20
[49], [{Pt(η2 - N,S- pyS)(en)}2]Cl2 21, 22 [50], [Pt2(en)2(η
2 - N,S- 4-MepyS)2]Cl2. 3H2O
23 [50]. In the Pd dinuclear complex, metal metal distances (2.595 – 2.848 Å) are long
[51].
Pd Pd
SNN S
20
PMe3 PMe3
Cl Cl
Pt Pt
SNN S
21,22
N NN N
ClPt Pt
SN
SNN
N
S
S
Cl
23
8
N N =
N S_
20 - 22
N S_
23
MeEthylene diamine
Cu and Ag
Reaction of CuCl2.2H2O with pySH in ethanol formed Cu(I) complex of
stoichiometry, CuCl(pySH), which on further reaction with two equivalents of Ph3P in
CHCl3 formed the product, [CuCl(η1 - S- pySH)(PPh3)2] 23 [52,53]. It has tetrahedral
geometry with strong NH∙∙∙Cl intramolecular hydrogen bonding. Copper(I) bromide
formed both mononuclear complex, [CuBr(η1-S- pySH)(PPh3)2] 24 as well as a dinuclear
complex, [Cu2(µ-S-pySH)2Br2(PPh3)2] 25 [54].
24
S
Cu
N
ClPh3P
PPh3
23
Cu Cu
S
SPh3P
Br
Br
HN
NH
25
PPh3
23 - 25
NH
S
H........
S
Cu
N
BrPh3P
PPh3
H........
9
Reactions of Copper(I) halides with pySH in the presence of a series of diphosphine
ligands {dppm, dppe, dppp, dppb, dppen} yielded interesting results. Copper(I) chloride
and bromide formed complexes: [CuX(pySH)(L-L)] 26 {X = Cl, Br, L-L = dppe, dppp,
dppb} [55]. For X = Br, L-L = dppe, it was shown to have structure [Cu2Br2(µ-P,P-
dppe)2(pySH)2] 27 [56]. Copper(I) iodide has formed an iodo-bridged hexanuclear Cu(I)
linear polymer, [Cu6(µ3-S- pySH)4(µ2-S- pySH)2(I)4(µ-I)2]n. 2nCH3CN 28 in the presence
of diphosphines (dppm, dppp, dppb, dppen) and with dppe it gave a trinuclear complex,
[Cu3I3(dppe)2(η1 - S- pySH)2] 29 [57].
26
S
Cu
NH
P
P
XHN
NH
Cu Cu
P
S
SBr
Br
27
P
P P
NH
CuCuI
I
P
P
Cu
P
P
P P
IS
NH
Cu
I
S
CuI
Cu
S
Cu
I
S
Cu
I
I
SS
S
Cu
I
28
NH
NH
HN HN
HN
29
10
26 - 29
NH
S
P P = dppe
Reactions of Cu(I) halides with substituted tertiary phosphines, namely, p-tolyl3P
and m-tolyl3P and pySH formed dinuclear complexes, [Cu2X2(µ - S- pySH)2(p-tol3P)2]
(X = Br, 30 [52]; I, 31 [58]), [Cu2Br2(µ - S- pySH)2(m-tol3P)2] 32 [59].
30 - 32
NH
S
Cu Cu
S
Sp-tol3P X
X
HN
NH
30, 31
P(p-tol)3
Cu Cu
S
Sm-tol3P Br
Br
HN
NH
32
P(m-tol)3
Reactions of silver(I) chloride/bromide with PPh3 in acetonitrile and pyridine – 2
– thione in CHCl3 in 1:1:1 ratio have yielded S - bridged dimers of general formula,
[Ag2X2(µ-S-pySH)(PPh3)2] {X = Cl, 33; Br, 34} [60]. The central Ag2S2 cores form
parallelogram with unequal Ag – S bond distances. The geometry is highly distorted
tetrahedral.
11
X = Cl 33, Br 34
Ag Ag
S
SPh3P
X
X
HN
NH
33, 34
PPh3
33, 34
NH
S
Hg
Organomercury(II) with pySH formed a complex, [PhHg(η1- S-pyS)] 31 [61]. In
this complex Hg is strongly bonded to one C and one S atom. This interaction is
relatively weaker than with N and very weak with second S atom of second molecule.
The geometry about Hg atom is distorted T-shaped. Another complex reported in
literature is: [MeHg(η1-S-pyS)] 32 [62]. In this complex, the ligand is unidentate,
bonding via S - donor atom. The geometry of the complex is trigonal bipyramidal,
considering long Hg∙∙∙S interactions with adjacent molecules.
N S_
31 - 32
Hg
N
S
C6H5
Hg
S
SS
N
Me
3231
Survey of literature with pyrimidine – 2 – thione and allied ligands
In this section, a survey of coordination chemistry of ruthenium(II), palladium(II),
platinum(II) and copper(I) with pyrimidine-2-thione (pymSH, II), 2-thiouracil (tucH2,
III), 2,4-dithiouracil (dtucH2, IV) and 6 – mercaptopurine (6-puSH2, V) is described.
12
N
NH
S
pymSH,II
N
N
N
NH
SH
6-puSH2,V dtucH2, IV
NH
NH
tucH2, III
O
NH
NH
S
7
8
9S S1 1 1
1
2 2 2 2
3 3 3
3
4 4 4
4
5 5 5 5
6 6 6
Pyrimidine - 2 - thione can coordinate to a metal ion via different donor atoms.
For example, neutral pyrimidine - 2 - thione shows S - bonding [VIa], while, anionic
pymS–
exhibits 1- S- bonding [VIb], N, S - chelation [VIc], N, S- bridging [VId], N, S-
chelation-cum-S-bridging [VIe], as well as N, S-bridging-cum-S-bridging [VIf]. Neutral
thiouracil shows S - bonding similar to VIa, while deprotonated tucH– shows S –
bonding, N, S- chelation and N, S- bridging similar to VIb, VIc and VId respectively.
Finally, neutral 6-mercaptopurine shows S - bonding similar to VIg, deprotonated puS–2
exhibits S - bonding and N, S- chelation similar to VIh and VIi respectively.
S
M M
S
MM
VIa VIb VIc
VId VIe
M
VIf
M
M
NH
N
N
N
SN
N
SN
N
M
SN
N
MM
SN
N
13
HN
N
N
NH
S
M
N
N
N
N
S
M
N
N
N
N
SM
VIg VIhVIi
The work is described under different sub-heads as follows:
Mo, W
Pyrimidine-2-thione and its derivatives have formed various types of complexes
with molybdenum [63-70] and tungsten [71-74]. A few examples are cited below:
[MoI(CO)3(η
2-N,S-dmpymS)] 33 [63], [Mo
IVO2(η
2-N,S-pymS)2] 34 [64], dimers
[Mo2II(η
2-N,S-dmpymS)4]2 35 [67] and [Mo
IIIO2(η
2-N,S-pymS)(py)]2 36 [68]. Complexes
are having N, S- chelation and N, S-bridging by the ligands. There is only one 2-
thiouracil complex, [MoII(Cp)2(η
2-N,S-tucH)](PF6) 37 [70].
Mo
S
NOC
CO
OC
33
Mo
N
S
N
S
O
O
34
Mo Mo
S
SN
N
NN
S
S
35
Mo
O
O
MoS
N
SN
pypy
O O 34, 3633, 35
36
N
N
CH3
H3C S_
N
N S_
14
Mo
N
S
37
NH
N
O
_S
37
+
Tungsten complexes are in 0, II and IV oxidation states. Pyrimidine - 2 - thione
formed, [Et4N][W(CO)4(η2-N,S-pymS)] 38 [71] and [W
II(CO)3(η
2-N,S-pymS)2] 39
complexes [72]. The anion of 38 has distorted octahedral structure, while 39 has
monocapped trigonal prism structure. With 2-thiouracil tungsten formed both distorted
tetrahedral, [WIV
(Cp)2(η2-N,S-tucH)]PF6 40 [70], and octahedral [Et4N][W
0(CO)5(η
1-S-
tucH)] 41, complexes [74].
Mn, Re
There is only one manganese complex, [MnII(η
2-N,S-dmpymS)2(phen)] 42 [75]
with a substituted pyrimidine - 2 - thione known so far.
N
N S_
-
38,39
W
N
S
N
S
COOC
CO
W
N
SOC
CO
CO
OC
3839
NH
N
O
_S
40,41
W
NS
OC
CO
CO
OC
CO
-
W
N
S
40
+
41
15
MnN
N
S
S
N
N
4242
N
N
CH3
H3C S_
Rhenium complexes with pyrimidine - 2 - thione and its derivatives [76-82], has
formed, mononuclear octahedral, [ReIII
Cl2(PPh3)2(η2-N,S-dmpymS)] 43 [76],
[ReIV
OCl2(PPh3)(η2-N,S-dmpymS)] 44 [76], and [Re
IVO(η
1-S-pymSH)(η
2-N,S-pymS)2]
45 [78], a distorted pentagonal bipyramidal, [ReIII
(PPh3)(η2-N,S-pymS)3] 46 [78] and
dinuclear [Re2(CO)8(µ-H)(µ-S-pymS)] 47 [80] and [(Re2O2(η2-N,S-dmpymS)4)O] 48
[81] complexes. In 47, two Re atoms are bridged through S of pymS- and H
- ion. In 48,
two Re atoms are bridged through O atom and the ligand is N, S- chelated. Only one
dinuclear complex of rhenium with uninegative 6-mercaptopurine, namely, [(Re2O2(η2-
N,S-puS)4O] 49 [83] is known so far. In this complex, two Re atoms are bridged
through O and the ligand is N, S- chelated.
PPh3Ph3P
Cl
Cl
Re
N
S
O
43 44
Ph3P
Cl
Cl
Re
N
S
S
HN
N
45
O
ReS
NS
16
S
N
Re
N
SN
S
46
Ph3PRe Re
S
H
N
CO
COCO
CO
CO
CO
OC
OC
47
O
ReSN
S N
O
ReSN
S N
O
48
O
ReSN
S N
O
ReSN
S N
O
49
N
N S_
45 -4743, 44, 48
N
N
CH3
H3C S_
49
N
N
N
NH
S-
Ru, Os
A number of mono- and tri- nuclear ruthenium complexes with pyrimidine - 2 -
thione and its derivatives have been updated [84-89]. A few examples are [Ru(bipy)2(η2-
N,S-pymS)](ClO4) 50 [84], [Ru(PPh3)2(η2-N,S-pymS)2]Cl2 2H3O
+ 51 [85], [Ru3(CO)9(µ-
S,N-dmpymS)H] 52 [86], [Ru3(CO)10(µ-S-dmpymS)2] 53 [86], [Ru3(CO)9(η1-S-
pymS)H] 54 [87]. In 50 and 51, octahedral complexes, the ligand is N, S- chelated, and
in trinuclear cluster 53, two Ru atoms are bridged through the S atom. In 52, 54, the
thioligands exhibit µ - S,N – bridging.
6-Mercaptopurine has formed octahedral complexes with ruthenium, viz.,
[Ru(bipy)2(η2-N,S-puSH2)]Cl2 55 [90] and [Ru(PPh3)2(η
2-N,S-puSH2)2](ClO4)2 56
17
[91].The oxidation state of ruthenium is II and the ligand is coordinated as neutral,
showing N, S- chelation.
+
NN
50
N
Ru
S
NN
PPh3
RuSN
S N
PPh3
51
2+
H
Ru
Ru RuS
COCO
CO
CO
CO
OC
OC
OC
OCN
52, 54
Ru
Ru Ru
S
COCO
CO
CO
CO
OC
OC
OC
OC CO
S
NN
53
Ru
S
S
N
N
2+
Ph3P
Ph3P
56
NN
N
RuS
NN
2+
55
18
N
N S_
50, 51, 54
52, 53
N
N
CH3
H3C S_
55,56
HN
N
N
NH
S
Only trinuclear osmium complexes with pyrimidine- 2- thione and its derivatives
have been reported, namely, [Os3(CO)9(µ-N,S-dmpymS)(µ-S-dmpymS)] 57 [92],
[Os3(CO)10(µ-S-dmpymS)2] 58 [92] and [Os3(CO)10(µ-S-dmpymS)H] 59 [93]. In 57,
dmpymS- shows mixed bonding, while in 58 and 59, it is µ - S - bridging.
S
Os
Os OsS
COCO
CO
CO
CO
OC
OC
OC
OCN
57
N
Os
Os Os
S
COCO
CO
CO
CO
OC
OC
OC
OC CO
S
NN
58
57 -59
N
N
CH3
H3C S_H
59
Os
Os Os
S
COCO
CO
CO
CO
OC
OC
OC
OC CO
N
Co, Rh
Cobalt has formed only octahedral complexes with pyrimidine - 2 - thione and its
derivatives [94-101], some of the examples are: [Co(η2-N,S-dmpymS)3] 60 [94, 95],
19
[Co(η2-N,S-mpymS)(en)2](ClO4)2
61 [96] and [Co(η
2-N,S-apymS)(en)2](ClO4)2 62 [97].
The oxidation state of Co is III and ligands are N, S- chelated in the complexes. The S-
atoms of the ligands are trans to each other in 60. 2-Thiouracil and 2,4-dithiouracil
(dtucH2) have yielded octahedral complexes, [Co(η2-N,S-tuc)(en)2](ClO4).H2O 63 [102]
and [Co(η2-N,S-dtuc)(en)2](ClO4)
64 [103]. The ligand 2-thiouracil and 2,4-dithiouracil
are coordinating as dianions.
Co
S
N
S
S
N
N
6061,62
Co
N
S
H2N
NH2
H2N
NH2
3+
Co
N
S
H2NNH2
H2N
NH2
3+
63,64
61 62
N
N
CH3
S_
H2N-CH2-CH2-NH2NH2H2N =
N
N
NH2
S_
63
N
N
O
_S
N
N
S
_S
64
_ _
60
N
N
CH3
H3C S_
Rhodium has formed mono- and di- nuclear square planar complexes with
pyrimidine - 2 - thione and its derivatives [104-106]. Some of the examples are,
[RhII(cp)(η
2-N,S-dmpymS)(η
1-S-dmpymS)] 65 [104], [Rh
I(CO)(η
2-N,S-
dmpymS)(PPh3)] 66 [105], [RhI(CO)2(η
2-N,S-dmpymS)] 67 [106], [Rh2
III(cp)2(µ
3-S,N-
mpymS)2](PF6)2 68 [106]. In 65, one ligand is bonded to Rh atom in 1- S mode and the
second ligand is in 2
– N, S chelation mode, in 66 and 67, it is N, S- chelated and in
68, the ligand is in µ3-S, N- mode.
6-Mercaptopurine with rhodium has formed octahedral complexes [RhIII
(η2-N,S-
puSH2)2(PPh3)(Ph)]Cl2. H2O 69 [107], and [RhIII
(η2-N,S-puSH2)(Ph)Cl2(SbPh3)] 70
[108] (SbPh3 = triphenyl stibine). The ligand is in N, S- chelation mode.
20
Rh
SS NN
65
PPh3
CO
Rh
N
S
CO
Rh
N
S
CO
66
67
Rh Rh
S
S
N
68
N
2+
2+
Ph
Rh
S
Ph
N
Cl
Cl
Ph3Sb
69 70
PPh3
RhSN
S N
65 - 67
N
N
CH3
H3C S_
68
N
N
CH3
S_
69,70
HN
N
N
NH
S
Ni, Pd and Pt
Pyrimidine - 2 - thione and its derivatives have formed a variety of complexes with
nickel [109-114], palladium [115-122], and platinum [123-127]. A few mono- and di-
nuclear complexes of Ni are: [Ni(η2-N,S-pymS)(bipy)2](SbF6) 71 [109],
[(CH3)3N(CH2Ph)]+[Ni(η
2-N,S-pymS)3]
- 72 [110], [(Ph)4P]
+[Ni(η
2-N,S-pymS)3]
- 73
[111]. The oxidation state of nickel is II and the ligand is showing N, S- chelation in 71 ,
72 and 73.
21
S
Ni
SS
N
N
+
71
72, 73
NN
N
NiS
NN
-
N
71 - 73
N
N S_
Several square planar PdII complexes are listed as follows: [Pd(η
2-N,S-dmpymS)2]
74 [115], [Pd(η1-S-pymSH4)4]Cl2.H2O 75 [116, 117], [Pd(η
2-N,S-pymS)(PPh3)2](ClO4)
76 [118], [Pd(µ-N,S-pymS)(PMe3)Cl]2 77 [119] and [Pd(µ-N,S-mpymS)(PMe3)Cl]2 78
[119] and [Pd2(µ-N,S-pymS)2(L)2] 79 [120] {L= (1-methyl imidazol - 2 – yl) ketone} . In
75, the ligand is neutral S- bonded, while in all other cases, the anionic ligands are N, S-
chelating or bridging.
There is one square planar complex of Pd with thiouracil, namely, [Pd2Cl2(PPh3)3(µ3-
N,N,S-tuc)] 80 [120] and one with 9-benzyl-6-mercaptopurine, [Pd(η2-N,S-bpuS)2] 81
[121]. In 80, the ligand is dinegative and coordinated as tridentate through three sites,
while in 81, the ligand is coordinated as uninegative anionic ligand via N7, S donor
atoms.
.
N
74
74
Pd
S S
N
N
N
CH3
H3C S_
NH
PdS
S S
S NH
HN
HN
NH
NH
S
75
75
2+
22
PPh3
PPh3
Pd
S
N
76
+Cl
Cl
Pd
Pd
N
NS
S
77, 78
L
L
N
N
Pd
Pd
N
N
S
N
79
S
N
N
NN
N
O CH3CH3
=
76, 77, 7978
N
N S_
N
N
CH3
S_
L = PMe3
(1-methyl imidazol - 2- yl) ketone
N N
Platinum(II) has formed square planar complexes, [Pt(η1-S-pymS)(terpy)](ClO4) 82
[123], [Pt(η2-N,S-dmpymS)2] 83 [124]. In octahedral complex, [Pt(η
2-N,S-mpymS)2Cl2]
N
N
PPh3
Pd
Ph3P Cl
Pd
Ph3P
Cl S
O
80
N
N
O
_S
80
_
81
81
NPd
S S
N
N
N
N
N
S-
CH2Ph
23
84 [124], the metal has IV oxidation state. Dinuclear PtIII
complexes are: [Pt2(µ-N,S-
pymS)4(η1-S- pymS)Cl] 85 [125, 126], [Pt2(µ-N,S-pymS)4X2] (X = Cl 86, Br 87, I 88)
[124, 127], and [Pt2(µ-N,S-tucH)4I2] 89 [126]. There are PtIII
- PtIII
bonds in 85-89. The
pyrimidine –2-thione and thiouracil ligand are uninegative and coordinate via N, S donor
atoms.
Pt
S N
N
N
N
PtSS
N N
8283
+
Cl
Cl
Pt
84
SN
S N
SCl NPt Pt
SN
SNN
N
S
S
85 X= Cl(86), Br(87), I(88)
XX Pt Pt
SN
SNN
N
S
S
IPt Pt
SN
SNN
N
S
S
I
89
83
N
N
CH3
H3C S_
N
N
CH3
S_
84
N
N S_
82, 85 - 88
NH
N
O
_ S
89
Cu, Ag and Au
Copper(I) halides, azide and thiocyanate salts have yielded several complexes with
pyrimidine - 2 - thione and its derivatives [128-142]. Some of the examples are:
[CuCl(η1-S-pymSH)(o-tol3P)] 90 [128], [Cu(η
1-S-pymSH4)2Cl] 91 [129], [Cu(η
1-S-
pymSH4)2Br] 92 [130], [CuX(η1-S-pymSH)(PPh3)2] {X = Cl, 93, Br, 94, I, 95} [131-
133], [Cu(η1-S-dmpymSH)(L)(PPh3)2] {L = N3, 96, NCS, 97} [134], [Cu(η
1-S-
pymSH)(dppp)X] {X = Cl, 98, Br, 99} [135], [CuBr(η1-S-pymSH)(L)] {L = o-
C6H4(PPh2)2} 100 [136], [CuCl(µ-S-pymSH)(p-tol3P)]2 101 [137], [Cu2X2(µ-S-
24
pymSH)2(η1-S-pymSH)2]2 (X = Cl, Br, and I, 102) [138], [CuX(µ-P,P-dppen)(η
1-S-
pymSH)]2 {X = Cl, 103, Br, 104, I, 105}[139 – 140]. In all the above complexes, the
ligands are neutral 1-S-bonded and the geometry around metal center is distorted
tetrahedral.
Cu
o-tol3P S
Cl
NH
90
o-tol3P = o-(CH3C6H4)3P
Cu
S S
X
NHHN
X = Cl 91, Br 92
S
Cu
NH
X = Cl 93, Br 94, I 95
XPPh3
PPh3
S
Cu
NH
L
L = N3, 96, SCN, 97
PPh3
PPh3PP = Ph2P(CH2)3PPh2 (dppp)
S
Cu
NH
P
P
X
X = Cl 98, Br 99
100
S
Cu
NH
P
P
Br
P P =PPh2
PPh2Cu Cu
S
Sp-tol3P Cl
Cl
HN
NH
101
P(p-tol)3
25
S
SI
Cu Cu
I
S
S
NHHN
NHHN
102
HN
NH
Cu Cu
S
SX
X
P P
P P
(X = Cl, 103, Br, 104, I, 105)
P P = dppen
NH
NH
S
91, 92
N
NH
S
90, 93-95,99-105
N
NH
CH3
H3C S
96, 97
Attempts to grow crystals of CuCl2(η1-S-tucH2)2 from DMF instead formed a
copper(I) complex, Cu(η1-S-tucH2)2Cl·DMF 106 [143,144]. The geometry around Cu(I)
center is essentially trigonal planar with the 1- S bonded neutral tucH2.
6-Mercaptopurine has yielded [Cu2(η1-Cl)2(µ-Cl)2(η
1-S- puSH3)2] 107, [Cu2(η
1-
Cl)4(µ-S- puSH3)2] 108 [145 - 146] The geometry around each Cu is tetrahedral. In
complex 107, Cl is bridging while in complex 108, ligand is bridging through S.
Cl
HN NH
Cu
SSNH
NH
O
S
106106
26
+HN
N
HN
NH
S
107-108
HN
NH
Cu Cu
Cl
Cl
S
SCl
Cl
107HN
NH
Cu Cu
Cl
Cl
S
S Cl
Cl
108
Both silver(I) [147-153] and gold(I, III) [154-159] have formed a variety of
complexes with pyrimidine - 2 - thione and its derivatives. With silver(I), pyrimidine –2-
thione has formed mononuclear, [Ag(PPh3)2(η1-S-pymS)]NO3 109 [147] and dinuclear,
[Ag2(µ-Br)2(PPh3)2(η1-S-pymSH)2] 110 complexes [148]. Gold(I) has formed mono- or
di- nuclear complexes: [Au(η1-S-pymS)(PPh3)] 111 [154], [Au(η
1-S-dmpymS)(PPh3)]
112 [155], [Au(η1-S-dmpymS)2] 113 [156], [Au(µ-N,S-dmpymS)]2 114 [156], [Au(µ-
N,S-pymS)]2 115 [156], [Au(η1-S-apymS)(PPh3)] 116 [157] and [Au(η
1-S-
apymS)(PEt3)] 117 [157]. The geometry around Au centre is linear.
S
Ag
N
PPh3Ph3P
109
Ag Ag
Br
BrS
S
NH
HN
PPh3
Ph3P
110
27
AuPh3P NS
Au
S
S
N
N
111
AuPh3P NS
112113
Au Au
S
S
N
N
114, 115
AuPh3P NS
116
AuEt3P NS
117
110
N
NH
S
N
N S_
109, 111, 114
112, 113, 115
N
N
CH3
H3C S_
NH2
N
N S_
116,117
Thiouracil and 6-mercaptopurine has formed linear gold(I) complexes [160 -
166], namely, [Au(η1-S-tucH)(PPh3)] 118 [162], [Au(η
1-S-tucH)(PEt3)] 119 [163],
[Au(η1-S-puS)(PPh3)] 120 [163,164] and [Au(η
1-S-puS)(o-tol3P)] 121 [165]. The
ligands are 1-S bonded in all these complexes. Only one square planar complex of
gold(III) with 6-mercaptopurine, viz, [Au(η2-N,S-puS)Cl(L)]Cl 122 {L= N, N-
dimethylammoniummethylphenyl}[166] is reported.
28
NH
N
O
S
118,119
AuPh3P NS
118
AuEt3P NS
119
-
AuPh3P NS
120
Auo-tol3P NS
121
AuS
NHN
N
N
NH
S
L
ClCl-
+
120 -122122
-
Zn, Cd and Hg
Pyrimidine - 2 - thione and its derivatives, have formed several complexes with
post - transition elements [167-175]. Complexes of zinc(II) are: [ZnCl2(η1-S-
dmpymSH)2] 123 [167], [Zn(η1-S-mpymSH)4](ClO4)2 124 [168], and [Zn(py)(η
2-N,S-
dmpymS)2] 125 [169] and that of Cd(II) are [Cd(η2-N,S-pymS)2(phen] 126 [173] and
[Cd2(µ3-N,S-pymS-6-CF3)2(η2-N,S-pymS-6-CF3)2] 127 [174]. Complexes 123, 124 have
distorted tetrahedral structures, while complex 125 has square pyramidal structure.
Cadmium complex 126 has octahedral structure, while 127 is a dimer with square
pyramidal geometry around each Cd center.
6- Mercaptopurine and 2 - thiouracil have also formed mono- and di-nuclear complexes
[176 -178], [Cd(η2-N,S-puS)2Cl2] 128 [176] and [Cd(η
2-N,S-puSH2)Cl2(OH2 )]2 129
[177].
29
Cl
S NHCl
123
ZnS NH
2+
124
S NH
ZnS NH
S NH
S NH
Zn
S
NN
S
py
125
S
Cd
N
N
S
126
N
N S
CdCd
N
S
SN
N
N
S
127
Cl
Cl
S
CdNN
S
Cl
CdCd
N
S
ClH2O Cl
N
S
OH2Cl
128 129
124
N
N
CH3
S
123, 125
N
N
CH3
H3C S_
126
N
N S_
127
N
N
CH3
F3C S_
128,129
HN
N
N
NH
S
30
There are several mercury(II) complexes with pyrimidine - 2 - thione and its
derivatives. Some of the examples are, [Hg(Me)(η1-S-pymS)] 130 [178], [Hg(Me)(η
1-S-
mapymS)] 131 [179], [Hg(Me)(η1-S-mpymS)2] 132 [180], [HgI2(η
1-S-pymSH4)] 133
[181], [HgX2(η1-S-pymSH4)2] {X = Cl, 134, Br, 135, I, 136, SCN, 137, CN, 138} [182],
[Hg2Br2(η1-S-pymSH)(PPh3)] 139 [183], [Hg2(µ-Cl)2(η
1-S-pymSH)2(PPh3)2] 140 [184].
In 140, Hg(II) ion is bonded to two P atoms, and two bridging Cl atoms, while the other
Hg(II) ion is bonded to two S- atoms of pyrimidine - 2 - thione ligands and two bridging
Cl atoms.
Hg
N
S
N
N
H3C
H2N S_
CH3
130130-132 131
N
N S_
132
N
N
CH3
S_
X = Cl 134, Br 135, I 136, SCN 137, CN 138
I
N
Hg
S
I
133-138133
134-138
X
SHN
HgS NH
X
NH
NH
S
Br
Br
PPh3
N
NH
SHg
S NH
139
PPh3
PPh3
SN Cl
Hg Hg
ClSN
140139, 140
31
4-Amino-2-thiouracil and 6- mercaptopurine have yielded complexes,
[HgCH3(η1-S-atucH)] 141 [185], and 6-mercaptopurine yielded [HgCl2(η
1-S-puSH2)2],
142 [186].
Hg
N
S
CH3
NH
N
O
_S
141 141
Sn and In
Tin(IV) and indium(III) have formed a few complexes with pyrimidine - 2 - thione
and its derivatives [187-193]. Some of the examples are: [Sn(Ph)3(η2-N,S-pymS)] 143
[187], [Sn(Ph)3(η2-N,S-dmpymS)] 144 [188], [Sn(Ph)2(η
2-N,S-dmpymS)2] 145 [188],
[Sn(Ph)2(η2-N,S-pymS)2], 146 [189], [Sn(CH3)2(η
2-N,S-pymS)2] 147 [190] and [In(η
2-
N,S-pymS)3] 148 [192]. The ligands are N, S-chelating in all these complexes.
Ph
Ph
Ph
N
S
Sn
143, 144
Sn
SN
S
N
Ph
Ph
145
N
S
Ph
Ph
Sn
S
N
146
HN
N
N
NH
S
Cl
Cl
142
Hg
S NH
142
S NH
32
N
SSn
S
N
CH3
CH3
147
S
In
SS
N N
N
148
144, 145
N
N
CH3
H3C S_
143, 146, 147
N
N S_
Background and plan of Work
This survey of literature reveals that coordination chemistry of pyridine-2-thione has
been extensively studied [30-62]. Lobana et al. [33-36,41,43,44,47,48,52,53,55,57,
58,60,61] have investigated coordination chemistry of palladium(II), platinum(II),
ruthenium(II) and copper(I) metal ions with pyridine-2-thione (pySH) as N, S- donor
ligands. Mono- and di- tertiary phosphines such as PPh3, Ph2P(CH2)nPPh2 (n = 1, dppm;
2, dppe; 3, dppp; 4, dppb) were used as co-ligands. Pyridine-2-thione in neutral form
coordinated through S (η1-S and µ-S modes) and as an anionic ligand it either acted as a
N, S- chelating agent, or as a S-donor.
It was intended to extend coordination chemistry of these metals with other
heterocyclic thioamides, namely, pyrimidine-2-thione and purine-6-thione. These latter
ligands have more than two donor atoms and could provide several coordination
possibilities. A survey of literature reveals that only limited coordination chemistry of
pyrimidine-2-thione and purine-6-thione ligands has been reported [84-87, 118, 119],
particularly with the tertiary phosphines as co-ligands.
Keeping the above background in view, it was planned to investigate coordination
chemistry of Ru(II), Pd(II), Pt(II) and Cu(I) using pyrimidine-2-thione and purine-6-
thione ligands.
33
N
NH S
HN
N
N
NH
S
pymSHpuSH2
In detail, it was planned to carry out reactions with the anticipated products as shown
below;
Palladium(II). The starting material PdCl2(PPh3)2 with pymSH and puSH2 could provide
various possibilities (1 – 4, 7 – 10). Likewise with diphosphines as co-ligands, complexes
of the types 5, 6, 11 and 12 were anticipated.
PdCl2(PPh3)2 +N
N S
H
PdCl2(L-L) +N
N S
H
Pd
PPh3S
N
P
P
dppm, dppe, dppp, dppbP P =
PPh3
L-L =
Pd
PPh3S
S PPh3
S N
+
Cl-N
N
Pd
PPh3S
SPh3P
N
NPd
PPh3S
SN N
N
N S_
=
Pd
S
S
N
N
Pd
S
N
+
Cl-P
P
1
2
3
4
56
34
PdCl2(PPh3)2 +
PdCl2(L-L) +
Pd
PPh3S
N
P
P
PPh3
Pd
PPh3S
S PPh3
N
N
Pd
PPh3S
SPh3P
N
N
Pd
PPh3S
SN N
7 - 9, 12
N
N
N
NH
S-
dppm, dppp, dppbP P =L-L =
N
N
N
N
SH
H
Pd
S
S
N
N
Pd
S
N
P
P
9 7
10 8
12 11
S N = N
N
N
N
S-2
10, 11
N
N
N
N
SH
H
Platinum(II). The behaviour similar to that of palladium(II) was anticipated (13 – 24).
N
N S
H
Pt
PPh3S
N PPh3
Pt
PPh3S
S PPh3
N
N
Pt
PPh3S
SPh3P
N
N
Pt
PPh3S
SN N
H2PtCl6 + 2PPh3 +
+
Cl-
13
1416
15
35
P
P
N
N S_
dppm, dppe, dppp, dppbP P =L-L =
Pt
S
S
N
N
Pt
S
N
P
P
S N =
H2PtCl6 + (L-L) +N
N S
H
+
Cl-
1718
P
P
19 - 21, 24
N
N
N
NH
S-
dppm, dppp, dppbP P =L-L =
Pt
S
S
N
N
Pt
S
N
P
P
24 23
S N = N
N
N
N
S-2
22, 23
N
N
N
N
SH
H
H2PtCl6 + (L-L) +
Pt
PPh3S
N PPh3
Pt
PPh3S
S PPh3
N
N
Pt
PPh3S
SPh3P
N
N
Pt
PPh3S
SN N
N
N
N
N
SH
H
2119
2220
H2PtCl6 + 2PPh3 +
36
Ruthenium(II). In case of RuII, complexes of the type 25 – 28 were expected.
RuCl2(PPh3)3 + 2N
N S
H
Et3N
- PPh3
RuCl2(L-L)2 + 2N
N S
H
Et3N
- (L-L)
PPh3
PPh3
S
Ru
P
S
N
N
P
S
Ru
S
N
N
25
26
dppm, dpppP P =L-L =
Ru2Cl3(dppb)3 + 2N
N S
H
Et3N
-2dppb
S
Ru
P
S
N
N
P
Ru(pymS)2(PPh3)2 + dppeEt3N
- PPh3
S
Ru
P
S
N
N
P
27
28
Copper(I). With this metal, complexes of the type 29 – 33 were anticipated.
CuX +N
N S
H
+ PPh3Cu Cu
Ph3P
PPh3
HN
S
X
X
S
NH
N
N S
H
S NH=
Cu
X
PPh3
PPh3
HN S
X = Cl, Br, I
+ 2PPh3
29
30
37
Cu Cu
Ph3P
PPh3
HN
S
X
X
S
NH
CuX ++ PPh3N
N
N
N
SH
H
Cu
X
PPh3
PPh3
HN S
Cu
N
PPh3
PPh3
S
- HX + 2PPh3
S NH N
N
N
NH
S-
N
N
N
N
SH
H
X = Cl, Br, I
=S N
=
25
32
33
29 - 31, 3332
From the above proposed reactions, about 30 complexes have been synthesized
These have been characterized using analytical data, IR spectroscopy, 1H,
13C and
31P
NMR spectroscopy. Eighteen complexes have been studied using single x-ray
crystallography. The details of complexes are described in Chapter 2 and their
experimental details are given in Chapter 3.