Ligand Rearrangement and Hemilability in R hodium(I) and Iridium(I) Complexes Bearing Terphenyl Phosphines

We describe the synthesis of a series of cationic rhodium(I) and iridium(I) compounds stabilized by sterically demanding phosphines that contain a terphenyl substituent, PMe 2 Ar' (Ar' = 2,6-diarylphenyl radical). Salt metathesis of metal precursors [MCl(COD)(PMe 2 Ar')] (M = Rh, Ir; COD = cyclooctadiene) with NaBAr F (BAr F = B(3,5-C 6 H 3 (CF 3 ) 2 ) 4 ) results in a series of cationic complexes in which the loss of the chloride ligand is compensated by the appearance of relatively weak π-interactions with one of the flanking aryl rings of the terphenyl substituent. The same experiments carried out with carbonyl compounds [MCl(CO) 2 (PMe 2 Ar')] led to the corresponding cationic carbonyl complexes, whose CO-induced rearrangement reactivity has been investigated, both experimentally and computationally. The differences in reactivity between rhodium and iridium complexes, and as a result of varying the sterics of terphenyl phosphines are discussed