Comparison of the Reactivity of M(allyl)₃ (M = Rh, Ir) with Donor Ligands

Reactions of M(allyl)₃ [M = Rh, Ir] with a variety of donor ligands have been investigated. While both complexes are unreactive toward “hard” N- and O-donor ligands, “soft” ligands such as tolylisothiocyanate, tertiary phosphines, CO, and aryl isocyanides are readily added. Whereas ligand additions to Rh(allyl)₃ are often accompanied by reduction of the Rh(III) center, analogous reactions with Ir(allyl)₃ afford stable trivalent products containing σ-allyl ligands. The molecular structures of several derivatives are presented, including Ir(σ-allyl)(π-allyl)₂(PPh₃), Ir(σ-allyl)₂(π-allyl)(PMe₃)₂, and Ir(σ-allyl)₃(C⋮N-2,6-Me₂C₆H₃)₃.