Synthesis and structure of a new phosphonium-1-indenylide (PHIN) ligand, 4,7-dimethyl-1-C9H4PMePh2, and of new PHIN complexes of rhodium and iridium

This paper describes the synthesis, properties and crystal structure of a new phosphonium-1-indenylide ligand, 4,7-dimethyl-1-C9H4PMePh2, and the syntheses of complexes of rhodium(I) and iridium(I) containing both the parent PHIN ligand, 1-C9H6PMePh2 (I) and 4,7-dimethyl-1-C9H4PMePh2 (II). The complexes [M(Z4-COD)(Z5-PHIN)]X (M = Rh, Ir; PHIN = I, II; COD = 1,5-cyclooctadiene; X = Cl, BF4) and [Rh(Z5-I)(PPh3)2]BF4 have been prepared and characterized by HR-ESM, elemental analyses and NMR spectroscopy. While [Ir(Z4-COD)(Z5-I)]Cl undergoes one or more chloride-induced exchange processes involving the COD ligand, the analogous complexes of rhodium and iridium with the more weakly coordinating BF4 counter anion exhibit no exchange processes. In contrast, [Rh(Z5-I)(PPh3)2]BF4 undergoes an exchange process involving the inequivalent PPh3 phosphorus atoms and which is rationalized using DFT calculations.