Kinetics of conversion of [Ir4(CO)11(PPh2AuPPh3)] into [Ir4(CO)10(µ-PPh2)(µ-AuPPh3)] and their structural characterization

Abstract

Deprotonation of [Ir₄(CO)₁₁(PPh₂H)]1 in the pressence of [Au(PPh₃)]PF₆ yields the novel species [Ir₄(CO)₁₁(PPh₂AuPPh₃)]2 which possesses a tetrahedral framework bearing a terminally bonded PPh₂AuPPh₃ ligand. Changing the order of addition of the reagents results in the formation of [Ir₄(CO)₁₀(µ-PPh₂)(µ-AuPPh₃)]4 with bridging phosphido and Au(PPh₃)⁺ units. Reaction of 4 with PPh₃ yields [Ir₄(CO)₉(PPh₃)(µ-PPh₂)(µ-AuPPh₃)]6, while with the more basic phosphine P(C₆H₄OMe-4)₃ substitution of the PPh₃ at the Au(PPh₃)⁺ unit occurs producing [Ir₄(CO)₁₀(µ-PPh₂){µ-AuP(C₆H₄PMe-4)₃}]. Deprotonation of [Ir₄(CO)₁₀(PPh₃)(PPh₂H)] in the presence of [Au(PPh₃)]PF₆ yields [Ir₄(CO)₁₀(PPh₃)(PPh₂AuPPh₃)], which undergoes rearrangement to 6. The kinetics of decarbonylation of compound 2 and give 4 has been investigated and a dissociative mechanism is suggested, confirmed by the activation parameters ΔH^‡= 135.6 ± 3.8 kJ mol^–1 and ΔS^‡= 81.2 ± 10.9 J K^–1 mol^–1.