Ligand Rearrangement and Hemilability in Rhodium(I) and Iridium(I) Complexes Bearing Terphenyl Phosphanes

The synthesis of a series of cationic rhodium(I) and iridium(I) compounds stabilized by sterically demanding phosphanes that contain a terphenyl substituent PMe2Ar (Ar = 2,6-diarylphenyl) is described. Salt metathesis of metal precursors [MCl(COD)(PMe2Ar)] (M = Rh, Ir; COD = cyclooctadiene) with NaBArF {BArF = B[3,5-C6H3(CF3)(2)](4)} resulted in a series of cationic complexes in which the loss of the chlorido ligand is compensated by the appearance of relatively weak interactions with one of the flanking aryl rings of the terphenyl substituent. The same experiments carried out with carbonyl complexes [MCl(CO)(2)(PMe2Ar)] led to the corresponding cationic carbonyl complexes, the CO-induced rearrangement reactivity of which was investigated, both experimentally and computationally. The differences in reactivity between rhodium and iridium complexes and as a result of varying the sterics of terphenyl phosphanes are discussed.