Diphenyl dithiophosphato- and dicyclohexyldithiophosphinato-complexes of rhodium(I)

Abstract

The reaction of [{Rh(CO)₂Cl}₂], [Rh(PPh₃)₃Cl], and [{Rh(cot)Cl}₂] with diphenyl dithiophosphate, (PhO)₂PS₂^–, and dicyclohexyldithiophosphinate, (H₁₁C₆)₂PS₂^–, ions gives neutral four-co-ordinate complexes [RhL₂(S–S)] and [Rh(cot)(S–S)][L = CO or PPh₃; cot =η-cyclo-octa-1,5-diene; S–S^–=(PhO)₂PS₂^– or (H₁₁C₆)₂PS₂^–]. On treating rhodium(I) dithio-bonded complexes with CO or PPh₃ no five-co-ordinate complex has been obtained but only some substitution products of the neutral ligand. 1,2-Bis(diphenylphosphino)ethane and 1,2-bis-(diphenylarsino)ethane, L–L, react, cleaving the metal–sulphur bonds and giving new cationic five-co-ordinate species, [Rh(L–L)₂CO](S–S). These easily lose their CO affording cationic [Rh(L–L)₂](S–S) and these complexes may also be obtained as tetraphenylborate salts. On bubbling CO through a CH₂Cl₂ solution containing [Rh(L–L)₂](S–S)[S–S^–=(H₁₁C₆)₂PS₂^–], neutral [Rh(CO)₂(S–S)] is formed. The possibility of identifying the mode of co-ordination of the dithio-ligands by i.r. spectra is briefly discussed. Some oxidative-addition reactions of [Rh(CO)₂(S–S)] complexes are also reported: [{Rh(CO)(S–S)X₂}₂] complexes have been obtained by treating [Rh(CO)₂(S–S)] with bromine or iodine, whereas the same reaction with Mel gives [Rh(CO)(COMe)(S–S)l].