Mehra, R. K.

Singh, B.

English

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Indian Journal of ChemistryVol. 15A. December 1977. pp. 1048-1050Studies on Dibenzyl Sulphide & Dibenzyl Selenide Complexes oflridiumCIII)B. SINGH & R. K. MEHRADepartment of Chemistry, Patna University, Patna 800005Received 3 December 1976; revised 22 June 1977; accepted 30 July 1977Iridium(I1I) complexes of the type Ir(L).Cla (where L = dibenzyl sulphide or dlbenzyl sele-nide) have been prepared and characterized on the basis of analytical, molecular weight andspectral studies. IR data indicate that the Iigands coordinate through sulphur or seleniumatoms of the C = S or C = Se groups respectively. Octahedral structures with meridionalconfigurations have been assigned to the complexes. vIr-CI, vIr-S and vIr-Se modes of vibra-tion have been assigned in the far infrared region of the spectra of the complexes.DIALKYL sulphide and selenide complexes of anumber of metal ions have been studied byseveral workersv". However, comparativelyless work has been done with aromatic sulphideor selenide ligandss-1o. Some complexes of dibenzylsulphide (DBS) have been reported by Paul Haakeet al.n-13 {RhCla[(PhCH2)2S]a} has been used-! as acatalyst for the hydrogenation of maleic acid andtrans-cinnamic acid, but thorough investigationson the complexing behaviour of this ligand have notbeen made. Still less work has been done with thecorresponding selenium ligand, dibenzyl selenide(DBSe). In view of this, we undertook studieson the synthesis and characterization of complexesof dibenzyl sulphide and dibenzyl selenide, and theresults on iridium(III) complexes are reported here.Materials and MethodsAll the chemicals used were of c.P. grade.Dibenzyl sulphide and dibenzyl selenide wereprepared by the methods described in the literaturei"and the products were analysed and their puritieschecked spectroscopically.Preparation of complexes - Iridium trichloride hy-drated (0·2 g) was dissolved in methanol (20 ml),the solution was filtered and the filtrate was treatedwith a similarly prepared solution of the ligand(0·6 g in 50 ml of methanol). The mixture wasrefluxed on a water-bath for 1 hr when yellow (forDBS complex) or orange (for DBSe complex) colouredprecipitate was obtained. This was filtered, washedwith 'water, ice-cold ethanol and finally with ether.The complex was recrystallized from hot methanol.It was dried in vacuo over anhydrous CaCI2.Microanalyses of the compounds were carried outat IIT, Kanpur. Analyses of metal ions-" andchlcrine-" were carried out using standard methods.Ir(DBS)3CI3: m.p. 1840 (Found: C, 53.5; H, 4'7;Cl, 10'9; Ir, 20·9. Calc.: C, 53·6; H, 4'4; Cl, 11'3;Ir, 20'4%).IR(DBSelaCla: m.p. 930 (Found: C, 46·9; H, 3'6;Cl, 9'3; Ir, 17·1. Calc.: C, 46·5; H, 3'8; Cl, 9'8;Ir, 17·7%).1048Results and DiscussionAnalytical data indicate that the complexes havethe stoichiometry MLaCl3 where M = lr(III) andL = DBS/DBSe. Both these complexes are solublein benzene, chloroform, hot ethanol and DMF.Their high solubility in most of the organic solventsand molecular weight determination (determinedcryoscopically in benzene) suggest their monomericnature. Their solutions in benzene are nonconductingindicating coordinated nature of the chlorides. Thecompounds are diamagnetic and hence they may beassigned octahedral structures.On the basis of IR band assignments-s of theanalogous compound, C6HsCH2CH2C6Hs' the bandsbetween 3000 and 3100 em"! in the spectrum (IRspectra of the complexes were recorded in KBrwhile those of the ligands were recorded using theirthin films on a Perkin-Elmer 521 instrument) ofC&HSCH2SCH2C6Hsmay also be assigned to aromatic'IC-H. Similarly bands in the range 2800-3000crrr+ may be assigned to 'IC-H (aliphatic) in DBSe.A comparison of the spectrum of C6HsCH2SCH2-C6HS and C&H5CH2CH2C6H5indicates that a mediumband at 1240 crrr? is present in the spectrumof the former but is absent in the spectra ofC&H5CH2CH2C6Hs as well as C6H5CH2SeCH2C6Hs'It is therefore, suggested that this band has majorcontribution from 'ICS. Sharp and strong bands arepresent at 756 and 702 crrr'! in the spectrum ofC6HsCH2CH2C6H5 which are due to five adjacenthydrogen atomsl9•20 of the monosubstituted phenylgroup. A doublet at 768, 758 crrr ! and a verybroad band in the range 720-690 crrr? (multiplet)are present in the spectrum of C6HsCH2SCH2C6H5'There are significant changes in the positionsand intensities of the bands in the spectrum ofIr(DBS)3CI3 due to coordination of the ligandthrough thioketo sulphur atom. Thus, the band at1240 cm+ in dibenzyl sulphide is considerablyreduced in intensity, the doublet (768, 758 em:") isreduced in intensity while the broad multiplet in theregion 720-690 crrr? becomes a very strong singletcentred at 700 crrr '. These changes, especially theSINGH & MEHRA: IRIDIUM(III) COMPLEXESred-shifting of the 720 crn! band, indicate coordina-tion of dibenzyl sulphide to Ir(III) through sulphur.Similar red-shifting, on coordination through sulphur,of organosulphur ligands have been reported21-26. Acomparison of the far infrared spectra of DBS andIr(DBS)3CI3 in the range 400-300 crrr? indicates thatthere are strong bands in the spectrum of the latterat 300, 315 and 325 crrr+ which are absent in thespectrum of DBS. Most probably these bands aredue to vIr-CI modes and the presence of threebands indicates10,27>28 that it is a mer-isomer of theoctahedral form. Several sharp and weak bandsare also noticed in the range 370-380 cm! in the~pectrum of Ir(DBS)3CI3 which are not presentm the spectrum of DBS. These may have contri-bution from vlr= S. A strong band observed at825 ern"! in the spectrum of DBSe is absent in thespectrum of DBS. Hence it may be assigned tovC=Se. Similarly two bands at 615 and 580 crrr+,present in the spectrum of DBSe but absent in thespectrum of DBS, may be assigned to Vas C-Se-Cand Vsym C-Se-C modes respectively. The vCSe~and of the free DBSe ligand almost disappearsIn t~e ~R spectrum of Ir(DBSeJaCla indicatingcoordination of DBSe through selenium. Similardisappearance of 615 and 580 cm+ bands of DBSeis also found on coordination of the ligand.In the region 300-250 crrr+, the IR spectrum ofIr(DBSeJaCla shows a number of strong multipletswhich are not present in the spectrum of DBSe.They may be due to vIr-Cl modes of vibrationand indicate that the six coordinated complex,Ir(DBSe)3C1a may have octahedral meridional con-figuration.The meridional configurations of Ir(DBS)aCla andIr(DBSe)3Cl3 are also supported by their PMRspectra (taken in CDCl3 using TMS' as standard).The PMR spectru~ of DBS shows a strong peakat 2·8 't" corresponding to ten aromatic protons andanother peak at 6·5 r corresponding roughly to fourmethylene protons. In addition to this, there is avery small peak at 5·5 't" which persists in thespect.rum and which may be due to some impurity.Multiple peaks at 5·6 and 7·1 't" are observed in thePMR spectrum of dibenzyl selenide.The PMR spectrum of Ir(DBShCI3 which shows acomplex peak at 2·82 ""t" corresponding to aromaticprotons, and two peaks centred at 5·48 and 6·1 't"respectively, with peak area ratio of 2: 1. The~wo. different peaks may be due to two CH2 groups~n different magnetic environments. This can happenIf Ir(DBS)3Cl3 has meridional octahedral structurein "Yhich the two axially coordinated DBS ligandsare In. o~e ma~netic environment while the equatorialDBS IS In a different magnetic environment (Fig. 1).It is clear from Fig. 1 that the axiallv coordinated4>CH2S group is adjacent to three chlorine atomswhile. equatorial 4>CH2S group is adjacent to twochlorine atoms.PMR spectrum of Ir(DBSe)3Cla also shows acomplex peak centred at 2·7 't" corresponding toaroI?atIc protons. The CHa region does not containa slr~gle peak as is expected for a facial isomer,bu~ It contai.ns complex multiplets in this region.ThIS change In the two CH2 peaks indicates largerFig. 1interaction in Ir(DBSe)3Cl3 as compared to that iniridium complex with DBS. Thus, Ir(DBSe)3CI3 mayprobably have meridional configuration. This is inagreement with the fact that various IrL3Cl3 com-plexes have been found to be meridional isomers2M8•The electronic spectra (recorded in DMF orabsolute ethanol) of Ir(DBS)3C1a and Ir(DBSelaClaare almost identical with a band at 30300 crrr ' andshoulders at 28500 and 21800 cm+. However, themolar extinction coefficients of the bands forIr(DBSe)3Cla are almost twice those for the bandsof Ir(DBS)3CI3. The meridional isomers of generalformula Ir(R2S)aCI3 generally show three bands28around 31000-32000 (e = 102-103), 29000 (e = 102-103)and 21000 cm! (e = 10-102). The positions andintensities of the electronic spectral bands ofIr(DBS)3CI3 and Ir(DBSelaCI3 are in agreement withthis and hence these may also have meridionalconfigurations. .Acknowledge mentThe authors are thankful to the authorities of theCSIR, New Delhi, for the grant of a junior researchfellowship to R. K. Mehra. They also thank theauthorities of the Chemistry Department, IIT,Kanpur, for far infrared spectra and Central DrugResearch Institute, Lucknow, for NMR spectra.References1. AHUJA, I. s. & SINGH, RAGHUBIR, Indian J. Chem., 12(1974). 107.2. NAKAMOTO, K., Infrared spectra of inorganic and co-ordination compounds (John Wiley, New York), 1964·,146.3. AHUJA, I. S. & RASTOGI, P., J. inorg, nucl, Chern., 32(1970), 1381-4. GUPTA, S. K. & SHRIVASTAVA, T. S., J. inorg. nucl. Chem.,32 (1970), 1611-5. CONTRER.-.S, G. & SCHMIT, R, J. inorg. nucl, cse«, 32(1970), 1295.6. BAILY, R A. & PETERSON, T. R, Can. J. cu»; 46(1968), 311.7. HEALTH, G. A. & MERTIN, R L., Aust. J. cu-«, 23(1970), 1721; COATES, G. E. & RlDT.EY, D., J. chem,Soc., (1964), 166.8. FERGUSSON, J. E. & LOH, K. S., Aust. J. Chern., 26(1973), 2615.9. FERGUSSON, J. E., KARRAN, J. D. & SEEVRATNAM, 5.,J. chem. Soc., (1965). 2627.10. AIRES, BARBARA E., FERGUSSON, J. E., HOWARTH,D. T. & MILLER, JOAN M., J. chem, Soc. (Al, (1971).1144.11. HAAKE, PAUL & TURLEY, PATRICIA C., J. Am. chem,Soc., 89 (1967), 4611.12. HAAKE, PAUL & TURLEY, PATRICIA C., J. Am. chem,Soc., 89 (1967), 4617.13. HAAKE, PAUL & TURLEY, PATRICIA C., Inorg, nucl.chem. Lett., 2 (1966). 173.14. JAMES, B. R, NG, F. T. T. & REMPEL, G. L., Lnorg,nucl, chem, Lett., 4 (1968), 197.15. SINGH, B. & MEHRA, R K., Indian J. Chem., 13 (1975),1194.1049INDIAN J.CHEM., VOL. 15A, DECEMBER 197716. RAY, PRAFULLA CHANDRA & ADHIKARI, NADIABEHARI,J. Indian chem, Soc., 9 (1932), 25!.17. TREADWELL, P. P. & HALL, W. T., Analytical chemistry,Vol. II (John Wiley, New York), 1935, 307.18. NAKANISHI, K., Infrared absorption spectroscopy (Holden-Day, San Francisco), 1964, 129.19. DYER, JOHN R, Application of absorption spectroscopyof organic compounds (Prentice-Hall, New Jersey),1965, 33.20. BELLAMY, L. J., The infrared spectra of complex mole-cules (John Wiley, New York), 1956, 65.21. SINGH, B., SINGH, R., CHOUDHARY, R V. & THAKUR,K. P., Indian J. Chem., 11 (1973), 174.105022. NAKAMOTO, K., Infrared spectra of inorganic and coordina-tion compounds (John Wiley, New vork), 1964, 146.23. CONTRERAS, G. & SCHMIDT, R., J. inorg, nucl, Chem.,32 (1970), 129.24. BAILEY, R A. & PETERSON, T. R, Can. J. Chem., 46(1968), 3119.25. HEATH, G. A. & MERTlN, R. L., Aust, J. Chem., 23(1970), 172!.26. AHUJA, I. S. & RASTOGI, P., J. inorg, nucl. Chem., 32(1970), 138!.27. CHATT, j., LEISiH, G. J., STORACE, A. P., SQUIRE, D. A. &STARKEY, B., J. chem. Soc. (A), (1971), 899.28. ALLEN, E. A. & WILKINSON, W., J. chem. Soc. (Dalton),(1972), 613.

Studies on Dibenzyl Sulphide & Dibenzyl Selenide Complexes of lridium(III)

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Studies on Dibenzyl Sulphide & Dibenzyl Selenide Complexes of lridium(III)

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