Indian Journal of Chemistry Vol. 21A. July 1982, pp. 728-729 Bridging Carbon Disulphide Complexes: Replacement of Nitrosyl by Carbon Disulphide from Rhodium Nitrosyl Complexes K K PANDEY· & R SAHEBt Department of Chemistry, University of Indore. Indore 452001 Received 3 October 1981; revised 23 November 1981; accepted 4 December 1981 Treatment of rhodium nitrosyl complexes [Rh(NO)X1L1J (X = CI or Br; L = PPh 3 or AsPh,) with carbon disulphide in chloroform results in the displacement of nitrosyl group and in the formation of bridged carbon disulphide complexes [RhX1L]2CS2' These dimers react with Lewis bases. L (like PPh, or AsPh,) to give [RhXL)zC(S) (SL) complexes. Probable structures have been suggested for the two types of complexes. Recently there has been considerable speculation in the study of reactions of transition metal nitrosyl complexes I. Recently Agarwala and Pandey have shown? that the nitrosyl group can be replaced by thionitrosyl group (NS) only in those nitrosyl complexes which exhibit vNO in the region 1500-1650 em -I in their IR spectra. Herein we wish to report the reactions of carbon disulphide with rhodium nitrosyl complexes and the formation of bridging carbon disulphide complexes. Very few bridging CS z complexes have been reported earlier:'. All the chemicals used were of reagent grade or of comparable purity. All the solvents were dried by standard procedures. distilled, and deaerated before use. All manipulations were performed in an atmosphere of purified argon. Rhodium nitrosyl complexes Rh(NO)XzL z (X = CI or Br; L = PPh 3 or AsPh 3 ) were prepared by literature methods". Reaction of Rh(NO)Cl 2 (PPh 3 h with carbon disulphide- The method indicated below was followed in all the cases. A chloroform solution (50 ml) containing Rh(NO)CI 2 (PPh 3 h (0.5 g) and carbon disulphide(5 ml) was stirred at room temperature for 36 hr. The colour of the reaction mixture changed to red-violet. The reaction mixture was concentrated to dryness under reduced pressure and the residue recrystallised from dichloromethane-hexane as brown coloured solid. Similar reactions of Rh(NO)XBr(PPh 3 h, Rh(NO)CIX(AsPh 3 h (X = CI or Br) and Rh(NO)Br 2(AsPh 3 h with carbon disulphide have been performed. tDepartment of Chemistry. Indian Institute of Technology, Kanpur 208016. 728 .. J Reactions of brown complexes with triphenylphosphine--Triphenylphosphine (0.14 g) was added to a stirred solution of the above brown complex (0.37 g) in CH 2 Cl 2 (30 ml). The solution was refluxed for I hr when the colour of the solution became greenish yellow. On addition of n-hexane a greenish-yellow complex [RhCI(PPh 3 )]z CS(SPPh 3 ) separated out which was centrifuged, washed with n- hexane and dried in vacuo. The analyses for chloride, bromide and sulphur were carried out by standard methods". Phosphorus and arseni~ in samples were estimated by decomposing these III the presence of sodium peroxide, sugar and sodium nitrate in the ratio 20:1:3 in a Parr bomb crucible,. extracting the melt with water, and solution neutralised with H 2 S0 4 , Excess of H 2 S0 4 (l ml) was ~dded and heated till SO 3 fumes evolved. After cooling It was diluted with water and filtered if necessary. In this solution, phosphorus was estimated as phospho- arnmoniummolybdate and arsenic by the iodometric method. In order to estimate rhodium", samples were decomposed with concentrated sulphuric acid and concentrated nitric acid. The solution was evaporated to I ml and extracted with water. Rhodium was estimated i~ _the water extract as [Co(NH 3 )6]3+ [Rh(N0 2 )6l . Analytical data for the complexes are listed in Table I. Reactions of carbon disulphide with Rh(NO)ClXL z (X = CI or Br) and Rh(NO)Br z L 2 (L = PPh 3 or AsPh 3 ) led to the formation of brown complexes of composition [RhCIXL]2 (CS 2 ) and [RhBr z L]2 (CS 2 ).SMPh 3 and OMPh 3 (M = P or As) were recovered from the washing. All these complexes are air stable, diamagnetic solids, soluble in benzene, dichloromethane and chloroform and insoluble in ethanol, hexane and ether. The conductivities of the complexes were found to be very low (AM =2 to 8 ohm -I ern? mol : ') ruling out the ionic character of these complexes. The molecular weights of [RhCI 2 L]z (CS 2 ) (L = PPh 3 or AsPh 3 ) determined cryoscopically in benzene were found to be 890 and 928 respectively. The IR spectra of the complexes recorded in KBr or CsI on Perkin-Elmer instrument, model 580, exhibited a sharp band at 1005 em -I due to vCS besides the characteristic bands of coordinated triphenylphosphine or triphenylarsine. The absence of band at 1630 cm- I indicated the replacement of NO group by CS z group. No definite structure can be given for these complexes. However, assuming a symmetric arrange- .I