FURTHER-STUDIES OF DIPHOSPHINE-BRIDGED AND DIARSINE-BRIDGED RHODIUM COMPLEXES

A convenient, new route to the diphosphine-bridged dimers [Rh2(CNR)4(Ph2PCH2PPh2)2]2+ via the addition of the diphosphine and the isocyanide to [(1, 5-cyclooctadiene)RhCl]2 is described. The analogous diarsine-bridged dimers [Rh2(CNR)4-(Ph2AsCH2AsPh2)2] [BPh4]2 are best prepared by adding an isocyanide to Rh2(CO)2Cl2(Ph2AsCH2AsPh2)2 followed by precipitation of the cation with sodium tetraphenylborate. Oxidative addition of iodine to [Rh2(CNR)4(Ph2AsCH2AsPh2)2]2+ produces rhodium(II) complexes, [Rh2I2(CNR)4(Ph2AsCH2AsPh2)2]2+, with direct Rh-Rh bonds. Addition of disulfides to [Rh2(CNR)4(Ph2PCH2PPh2)2]2+ can produce two different products. With trifluoromethyl disulfide, rhodium(II) dimers, [Rh2(SCF3)2(CNR)4(Ph2PCH2PPh2)2]2+, are formed while with phenyl disulfide, pentafluorophenyl disulfide, and phenyl diselenide, rhodium(III) monomers, [Rh(SR)2(CNR)2(Ph2PCH2PPh2)]+ or [Rh(SePh)2(CNR)2(Ph2PCH2PPh2)]+, are obtained. Addition of disulfides and diselenides to Rh(CNR)4+ produces six-coordinate rhodium(III) species, trans[Rh(SR)2(CNR)4]+ or trans-[Rh(SePh)2(CNR)4]+. © 1979, American Chemical Society. All rights reserved.