Indian Journal of Chemistry Vol. 26A, June 1987, pp. 516-518 Uranium (IV)- (VI ) Mixed Valence Complex & Uranyl Complexes with Triethylenetetramine M B KOKARE & T KESAVADAS· Chemistry Division, Bhabha Atomic Research Centre, Trombay, Bombay 400085 Received 30 June 1986; revised 6 October 1986; accepted 17 Nocember 1986 Complexes of the compositions U'2vUv'02C1lo(trienh, [UCI.(0.5 trien»n, U0 2 C1 2 (trien) and U0 2 (NO J h (trien), (where trien = triethylenetetramine) have been synthesised, and characterised on the basis of IR and visible spectra, molar conductances and analytical data. Tentative structures have been assigned to the complexes on the basis of these studies. The reactions of aliphatic amines with uranium(lV) and uranyl compounds to form complexes have been studied by several workers' .-6. However, complexes with only a few polydentate aliphatic amines have been studied so far l . 5 . 6 . Herein we report the isolation and structure elucidation of the complexes formed by the reaction of the tetradentate ligand, triethylene- tetramine( trien) with UCI~, U0 2 CI 2 and U0 2 (N0 3 )2' 6H 2 0. The ligand and solvents used were rigorously dried by standard methods and distilled under moisture and oxygen-free conditions. Uranium tetrachloride was prepared? from nuclear grade UOiN0 3 h.6H 2 0 and was purified by sublimation. Dioxouranium dichloride was obtained by the reaction of oxygen with UCI~ at 300-350'C. The, preparation and handling of the complexes were carried out in a glove box continually flushed with dry argon/nitrogen. The' complex U~\UVI02C1lo (tricn); was prepared by dropwise addition of a solution of trien (3 mmol) in THF( 10 ml) to a solution of UCI.d3 mmol) in THF(30 ml). The reaction mixture was stirred for I hr and the pale green precipitate formed filtered off, washed with THF, and dried in /IQCUO to furnish a greenish grey solid. This complex was also obtained when a suspension of powdered UCI~.3THF in benzene was stirred with trien in I: I mol ratio for about 6 hr; yield, quantitative [UCI~(O.5 trienj], was prepared by stirring powdered UCI~ (5 mmol) with a solution of trien (15 mmol) in benzene for about two days; yield, quantitative. The complexes U0 2 CI 2 (trien) and UOiN0 3 h(trien) were prepared by the reaction of trien (3 mmol) with U0 2 CI 2 (3 mmol) and UOiN0 3 )z.6H 2 0 (3 mmol) respectively in THF medium. The reaction mixture was stirred for I hr and the precipitates obtained filtered 00; yield, quantitative. The nitrato compound was soluble in DMF, DMSO, nitromethane and nitrobenzene while the other complexes were soluble only in DMF and DMSO. The analytical data of the complexes are given in Table 1. U ranium(lV) was estimated volumetrically by dissolving the complex in 5% H 2 S0 4 followed by addition of excess of eerie sulphate and back titrating the excess of eerie sulphate with ferrous ammonium sulphate. The IR spectra of the complexes were recorded in nujol on a Perkin-Elmer grating spectrophotometer, model 577, using CsI plates. Molar conductances were measured at room temperature on a Wissenshaftlich Technische Werkstatten 08120 conductivity meter. The electronic spectrum of U~\UVI02Cllfi (trien), in 5/~ H 2 S0 4 (the complex was not stable in OMF and DMSO as mentioned later), in the visible region, exhibited absorption bands characteristic of both Complex Colour Table I -Analytical Data of the Complexes Decornp. Found (Calc), ':0 temp. _._- - ------- ( C) U(lV) U(VI) CI N N C H (organic) (nitrate) -190 30.7 16.0 23.4 10.7 13.7 4.1 (30.9) (15.5) (23.1) (10.9) (14.0) (3.5) -130 52.8 31.1 5.8 7.2 1.9 (52.6) (31.3) (6.2) (7.9) (2.0) -120 48.4 14.2 11.1 15.1 4.3 (4K.8) (146) (11.5) (14.8) (3.7) -120 43.3 10.5 5.3 13.1 3.6 (441) (10.4) (5.2) (13.3) (3.3) [UCI J(trien)] 2 [U0 2 C1 4 (trien)] [UCI.(0.5 trienj], Greenish Grey Olive green Yellow [UO,(lrien)]- [UO:CI.(trien)] U0 2 (NO J h(lrien) do SUi
Transcript
Indian Journal of ChemistryVol. 26A, June 1987, pp. 516-518
Uranium (IV)- (VI )Mixed ValenceComplex & Uranyl Complexes with
Triethylenetetramine
M B KOKARE & T KESAVADAS·Chemistry Division, Bhabha Atomic Research Centre, Trombay,
Bombay 400085
Received 30 June 1986; revised 6 October 1986;accepted 17Nocember1986
Complexes of the compositions U'2vUv'02C1lo(trienh, [UCI.(0.5trien»n, U02C12 (trien) and U02(NOJh (trien), (where trien =
triethylenetetramine) have been synthesised, and characterised onthe basis of IR and visible spectra, molar conductances andanalytical data. Tentative structures have been assigned to thecomplexes on the basis of these studies.
The reactions of aliphatic amines with uranium(lV)and uranyl compounds to form complexes have beenstudied by several workers' .-6. However, complexeswith only a few polydentate aliphatic amines have beenstudied so farl.5.6. Herein we report the isolation andstructure elucidation of the complexes formed by thereaction of the tetradentate ligand, triethylene-tetramine( trien) with UCI~, U02CI2 and U02 (N03)2'6H20.
The ligand and solvents used were rigorously driedby standard methods and distilled under moisture andoxygen-free conditions. Uranium tetrachloride wasprepared? from nuclear grade UOiN03h.6H20 andwas purified by sublimation. Dioxouranium dichloridewas obtained by the reaction of oxygen with UCI~ at300-350'C. The, preparation and handling of thecomplexes were carried out in a glove box continuallyflushed with dry argon/nitrogen.
The' complex U~\UVI02C1lo (tricn); was preparedby dropwise addition of a solution of trien (3 mmol) inTHF( 10 ml) to a solution of UCI.d3 mmol) in THF(30
ml). The reaction mixture was stirred for I hr and thepale green precipitate formed filtered off, washed withTHF, and dried in /IQCUO to furnish a greenish greysolid. This complex was also obtained when asuspension of powdered UCI~.3THF in benzene wasstirred with trien in I: I mol ratio for about 6 hr; yield,quantitative
[UCI~(O.5 trienj], was prepared by stirringpowdered UCI~ (5 mmol) with a solution of trien (15mmol) in benzene for about two days; yield,quantitative.
The complexes U02CI2 (trien) andUOiN03h(trien) were prepared by the reaction oftrien (3 mmol) with U02CI2 (3 mmol) andUOiN03)z.6H20 (3 mmol) respectively in THFmedium. The reaction mixture was stirred for I hr andthe precipitates obtained filtered 00; yield,quantitative.
The nitrato compound was soluble in DMF,DMSO, nitromethane and nitrobenzene while theother complexes were soluble only in DMF andDMSO.
The analytical data of the complexes are given inTable 1. U ranium(lV) was estimated volumetrically bydissolving the complex in 5% H2S04 followed byaddition of excess of eerie sulphate and back titratingthe excess of eerie sulphate with ferrous ammoniumsulphate. The IR spectra of the complexes wererecorded in nujol on a Perkin-Elmer gratingspectrophotometer, model 577, using CsI plates.Molar conductances were measured at roomtemperature on a Wissenshaftlich TechnischeWerkstatten 08120 conductivity meter.
The electronic spectrum of U~\UVI02Cllfi (trien), in5/~ H2S04 (the complex was not stable in OMF andDMSO as mentioned later), in the visible region,exhibited absorption bands characteristic of both
Yellow[UO,(lrien)]-[UO:CI.(trien)]U02(NOJh(lrien) do
SUi
U(IV) species [at 425, 485, 492 (sh), 547 and 652 nm]and uranyl species [shoulders at 400 and 410 nm on the425 nm U(IV) band]. The IR spectrum of the complexexhibited v••(O- U -0)8, 15(0- U -0)8 and V(U- CI)2 modes at 915, 255 and 242 em -I, respectively.The bands which appeared at 580 and 520 em -I wereassigned to vU - N mode". The ligand modes ofcoordinated trien were analogous to those reported forrelated ligands!", and were closely similar for all thetrien complexes reported in this work. Thecomposition of U~vUv'02CllO (trien), could cor-respond to a 2:1 mixture of UCl4 (trien) and U01Cl1(trien). In the absence of characteristic features ofU01Cl2 (trien) in the IR spectrum, the complex istentatively' formulated as [U'VClitrien)]i [UV'02Cl4(trienj]? -. A similar complex, [U'VCl(DMf)7]~+[UV'02CI4]~ - has been isolated from the reactionbetween UCl4 and DMF in acetone 1I.
The nature of the reactions between UCl4 and trienin THF /benzene leading to the formation ofU~vUv'02CllO (trien), and [UCI4(0.5 trieni], suggestsoxygen abstraction from THF by U(IV). The molarconductance of U~vUV'02CllO(trienh in DMF (145.0ohm -lcm2mol--1 at 10 -3 M) indicated it to be a 2:1electrolyte I2, in conformity with the above for-mulation although the visible spectrum of the solutionindicated oxidation of U(IV) to uranyl. species. Similaroxidation was also observed in DMSO solution. Themagnitude of molar conductance was very close to thatof the 2:1 electrolyte [ClOH9N2]2 [U02CI4]13 inDMF solution (AM = 150.0 ohm-1cm1mol-1 of10 -3 M solution, as measured in this work). Thissuggests oxidation of the unipositive U(lV) species inthe complex to unipositive uranyl species of the type[U01CI(trien)] + possibly by oxygen abstraction fromthe solvent.
The complex [UCl~(0.5 trienj], exhibited in its IRvU -CI and vU - N modes at 230, and 520 and 560cm -I respectively. This complex was found to undergooxidation to uranyl species on dissolution both inDMF and DMSO. A tentative structure involvingbridging between- two UCl4 groups by a trien molecule,or a polymeric structure with chlorine bridgingbetween these dinuclear species is suggested for thiscomplex.
The IR spectrum of U02CIz(trien) displayed twostrong bands, at 915 and 880 em - 1, attributable to Vas
(0 - U - 0) mode. Since this mode is non-degeneratethe appearance of two bands indicates the presence oftwo types of uranyl species in the complex. The <XO- U -0) and vU - CI modes were observed at 255 and240 em -I respectively and the vU - N mode at 570em -I. The molar conductance of 10-3 M solution ofthe complex in DMF (72.0 ohm -lcm1mol- I)calculated with formula weight of U02CI2(trien) as the
NOTES
140
BO
Fig. I-Variation of Aeq with "/Ceq for (a) UOiNO~itrien)and(b)U02Clitrien) in DMF solution
molecular weight was indicative of a 1:1 electrolyte'P,However, it was found that the slope of the plot of Aeqagainst JCeq (Ceq = equivalent concentration) wasgreater than that for 1:2 electrolytes [likeUOiN03)z(trien) in DMF (Fig. 1), and othercomplexes+" in nitromethane], indicating that thecharge on the conducting species exceeds unity='. Onthe basis of this observation and the IR spectralevidence the complex is tentatively formulated as[UOitrien)]2 +-[U01Clitrien)]2 -.
The IR spectrum of U02(N03}z(trien) exhibitedvasCO - U -0),15(0 - U -0) and v(U -ON02) modesat 900, 255 and 262 (sh) em --I respectively, and the vU- N mode at 580 cm -I. The fundamental NO; bandsdiagnostic of the coordination mode of this group wereobscured by the bands due to trien in the region 1200-1500 em -I. Two weak combination bands due to N03-were observed at 1750 and 1735 em -I, the frequencyseparation of which indicated monodentate nitratecoordination 15. The complex was found to be a 1:2electrolyte in DMF (AM = 136.0 ohm -Icmlmol-I;10 -3M solution) while in nitromethane it behaved as aweak electrolyte+ (AM = 24.0 ohm -lcm2mol-l;10 -3 M). The monodentate coordination of N03-
in the complex is worth noting since bidentate NO;ligands have been observed in most. of the uraniumcompounds 16.
The authors are thankful to Dr R M Iyer for his keeninterest in the work and to Dr M Sankar Das and Dr MS Chadha for providing C and H analyses.
1385.2 Brown D, in Inorganic chemistry, Series One Vol 7; MTP
international review of science, edited by K W Bagnall(Butterworths, London) 1972.
3 Gans P & Marriage J, J chem Soc Dalton Trans, (1972) 1738.4 Cinquantini A, Zanello P, Mazzocchin G A & Traverso 0, Inorg
chim Acta, 25 (1977) 141.5 Zanello P, Cinquantini A, Seeber R & Pieri G, Inorg chim Acta 29
(1978) 171.6 Syamal A, Singhal 0 P & Ahmad S, Indian J Chern, 21A (1982)
193.
517
INDIAN 1.CHEM., VOL. 26A, JUNE 1987
7 Khan 1A & Ahuja H S, in Inorganic Synthesis, edited by John PFackler (Jr) (John Wiley, New York) 1982, p 187.
8 Vidali M, Vigato P A & Casellato U, J inorg nucl Chem, 37 (1975)955.
9 Watt G W & Klett D S, Inorg Chem, 5 (1966) 1278.10 Cotton F A, in Modern coordination chemistry, edited by J Lewis
& R G Wilkins (Interscience, New York) 1960.
518
11 Kepert D L, Patrick J M & White A H, J chem Soc Dalton Trans,(1983) 381.
12 Geary W J, Coord chem Rev, 7 (1971) 81.13 Markov V P & Tsapkin V V, Russ J inorg Chem, 4 (1959) 1030.14 Westland AD & Pluscec J, Can J Chem; 46(1968)2097.15 Lever A 8 P, Mantovani E & Ramaswamy 8 S, Can J Chem, 49
