bridging carbon disulphide complexes: …nopr.niscair.res.in/bitstream/123456789/51748/1/ijca...

Indian Journal of ChemistryVol. 21A. July 1982, pp. 728-729

Bridging Carbon Disulphide Complexes:Replacement of Nitrosyl by CarbonDisulphide from Rhodium Nitrosyl

Complexes

K K PANDEY· & R SAHEBtDepartment of Chemistry, University of Indore. Indore 452001

Received 3 October 1981; revised 23 November 1981; accepted 4December 1981

Treatment of rhodium nitrosyl complexes [Rh(NO)X1L1J (X =CIor Br; L= PPh3 or AsPh,) with carbon disulphide in chloroformresults in the displacement of nitrosyl group and in the formation ofbridged carbon disulphide complexes [RhX1L]2CS2' These dimersreact with Lewis bases. L (like PPh, or AsPh,) to give [RhXL)zC(S)(SL) complexes. Probable structures have been suggested for the twotypes of complexes.

Recently there has been considerable speculation in thestudy of reactions of transition metal nitrosylcomplexes I . Recently Agarwala and Pandey haveshown? that the nitrosyl group can be replaced bythionitrosyl group (NS) only in those nitrosylcomplexes which exhibit vNO in the region 1500-1650em -I in their IR spectra. Herein we wish to report thereactions of carbon disulphide with rhodium nitrosylcomplexes and the formation of bridging carbondisulphide complexes. Very few bridging CSzcomplexes have been reported earlier:'.

All the chemicals used were of reagent grade or ofcomparable purity. All the solvents were dried bystandard procedures. distilled, and deaerated beforeuse. All manipulations were performed in anatmosphere of purified argon. Rhodium nitrosylcomplexes Rh(NO)XzLz (X = CI or Br; L = PPh3 orAsPh3) were prepared by literature methods".

Reaction of Rh(NO)Cl2 (PPh3h with carbondisulphide- The method indicated below was followedin all the cases.

A chloroform solution (50 ml) containingRh(NO)CI2(PPh3h (0.5 g) and carbon disulphide(5 ml)was stirred at room temperature for 36 hr. The colourof the reaction mixture changed to red-violet. Thereaction mixture was concentrated to dryness underreduced pressure and the residue recrystallised fromdichloromethane-hexane as brown coloured solid.

Similar reactions of Rh(NO)XBr(PPh3h,Rh(NO)CIX(AsPh3h (X =CI or Br) andRh(NO)Br 2(AsPh3h with carbon disulphide have beenperformed.

tDepartment of Chemistry. Indian Institute of Technology, Kanpur208016.

728

..J

Reactions of brown complexes withtriphenylphosphine--Triphenylphosphine (0.14 g) wasadded to a stirred solution of the above browncomplex (0.37 g) in CH2Cl2 (30 ml). The solution wasrefluxed for I hr when the colour of the solutionbecame greenish yellow. On addition of n-hexane agreenish-yellow complex [RhCI(PPh3)]z CS(SPPh3)

separated out which was centrifuged, washed with n-hexane and dried in vacuo.

The analyses for chloride, bromide and sulphur werecarried out by standard methods". Phosphorus andarseni~ in samples were estimated by decomposingthese III the presence of sodium peroxide, sugar andsodium nitrate in the ratio 20:1:3 in a Parr bombcrucible,. extracting the melt with water, and solutionneutralised with H2S04, Excess of H2S04 (l ml) was~dded and heated till SO 3 fumes evolved. After coolingIt was diluted with water and filtered if necessary. Inthis solution, phosphorus was estimated as phospho-arnmoniummolybdate and arsenic by the iodometricmethod.

In order to estimate rhodium", samples weredecomposed with concentrated sulphuric acid andconcentrated nitric acid. The solution was evaporatedto I ml and extracted with water. Rhodium wasestimated i~ _the water extract as [Co(NH3)6]3+[Rh(N02)6l . Analytical data for the complexes arelisted in Table I.

Reactions of carbon disulphide with Rh(NO)ClXLz(X =CI or Br) and Rh(NO)BrzL2 (L = PPh3 or AsPh3)

led to the formation of brown complexes ofcomposition [RhCIXL]2 (CS2) and [RhBrzL]2(CS2).SMPh3 and OMPh3 (M = P or As) wererecovered from the washing.

All these complexes are air stable, diamagneticsolids, soluble in benzene, dichloromethane andchloroform and insoluble in ethanol, hexane and ether.The conductivities of the complexes were found to bevery low (AM =2 to 8 ohm -I ern? mol : ') ruling outthe ionic character of these complexes. The molecularweights of [RhCI2L]z (CS2) (L = PPh3 or AsPh3)

determined cryoscopically in benzene were found to be890 and 928 respectively. The IR spectra of thecomplexes recorded in KBr or CsI on Perkin-Elmerinstrument, model 580, exhibited a sharp band at 1005em -I due to vCS besides the characteristic bands ofcoordinated triphenylphosphine or triphenylarsine.The absence of band at 1630 cm-I indicated thereplacement of NO group by CSz group.

No definite structure can be given for thesecomplexes. However, assuming a symmetric arrange-

. I

NOTES

Table 1- Melting Points and Analytical Data of the Complexes

Complexes m.p. Found (Calc.) (%)°C

C H S CI/Br P/As Rh

[RhCIz(PPh)h (CS2) >280 46.6 3.1 6.9 15.2 6.6 21.4

(46.8) (3.1) (6.7) (14.9) (6.5) (21. 7)

[RhC IBr(PPh)] 2(CS J >280 42.9 2.7 6.1 22.5 5.9 19.5(42.8) (2.9) (6.2) (22.3) (6.0) (19.9)

[RhBr2(PPh)}]2(CSZ) >280 39.4 2.9 6.0 28.8 5.3 18.4(39.4) (2.7) (5.7) (28.4) (5.5) (18.3)

[RhCl2(AsPh)]2(CS2) >280 43.0 2.8 6.0 14.0 14.3 19.7(42.9) (2.9) (6.2) (13.7) (14.5) (19.9)

[RhCIBr(AsPh)Jz(CSz) >280 39.4 2.7 5.8 20.8 13.5 18.0(39.5) (2.7) (5.7) (20.5) (13.3) (18.3)

[RhBr 2(AsPh)]iCSz) >280 36.6 2.6 5.5 26.6 12.4 16.8(36.6) (2.5) (5.3) (26.3) (12.3) (17.0)

[RhCI(PPh))]2CS(SPPh)) 152 66.1 4.0 5.6 6.5 8.3 18.4(66.0) (3.9) (5.6) (6.2) (8.2) (18.1)

[RhBr(PPh))]2CS(SPPh)) 148 61.2 3.5 5.4 13.3 7.2 16.5(61.2) (3.7) (5.2) (13.0) (7.6) (16.8)

[RhCl(AsPh))]2CS(SPPh)) 168 61.4 3.5 5.1 6.0 17.0(61.3) (3.7) (5.2) ( 5.8) (16.8)

[RhBr(AsPh)]2CS(SPPh) 160 57.0 3.4 4.9 12.4 15.8(57.1) (3.4) (4.7) (12.1) (15.6)

S(PPhJ) CI2Fltf "FlhCI2(PPhJ)

"c/S(I)

PPhJ

(PPhJ) CIRt('S'FlhCI (PPhJ)'c/S

(lJ)

ment for the two [RhCI2L] moieties, bridging of thetype Rh - S =C =S - Rh or of the type shown instructure (I) would be possible 7. The complexes arediamagnetic suggesting the oxidation state of rhodiumin these complexes to be + 3. Since the four coordinatedrhodium(III) complexes are not stable, the firstpossibility can therefore be ruled out.

Further the reactions of these complexes with PPh3

afforded complexes of the type [RhXL]2CS(SPPh3)with the reduction of Rh(III) to Rh(I). The IR spectraof these complexes exhibited vCS, v Rh-Cl (terminal Clgroup) and vP-S at 1005, 340 and 545 cm :'

respectively, consistent with structure (II) for thesecomplexes.

We are grateful to Prof. V.c. Agarwala,Department of Chemistry, I.I.T. Kanpur fornumerous stimulating conversations.

ReferencesI McCleverty J A, Chem Rev, 75 (1979) 53.2 Pandey K K & Agarwala U C, Inorg Chem, 20 (1981) 1308.3 Y anefT P V, Coord Chem Rev, 23 (1977) 183; Arrnit P W, Sirne W J

& Stephenson T A, J organometal Chem, 161 (1978), 391;Oehmichen U, Southern T G, LeBozec H & DixneufP J, Jorganometal Chem, 156(1978) C-29; Werner H, Leonhard K& Bursech Ch, J organometal Chem, 160 (1978) 291.

4 Pandey K K & Agarwala U C, Z anorg a//g Chem, 457 (1979) 235;Pandey K K, Datta S & Agarwala U C, Transition MetalChem, 4 (1979) 337; Pandey K K & Agarwala U C, J inorgnucl Chem, 42 (1980) 293.

5 Vogel A I, A textbook of quantitative inorganic analysis(Longmans Green, London) 1961.

6 Beamish F E, A textbook of analytical chemistry of noble metal(Pergamon, Oxford) 1966.

7 Butler I S, Coville N J & Cozec D J, J organometal Chem, 133(1977) 52.

729