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

Abstract

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(η⁴-COD)(η⁵-PHIN)]X (M = Rh, Ir; PHIN = I, II; COD = 1,5-cyclooctadiene; X = Cl, BF₄) and [Rh(η⁵-I)(PPh₃)₂]BF₄ have been prepared and characterized by HR-ESM, elemental analyses and NMR spectroscopy. While [Ir(η⁴-COD)(η⁵-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(η⁵-I)(PPh₃)₂]BF₄ undergoes an exchange process involving the inequivalent PPh₃ phosphorus atoms and which is rationalized using DFT calculations.