Construction of trinuclear iridium clusters through ancillary ortho-carborane-1,2-diselenolato ligands, with simultaneous iridium-induced B–H activation

Abstract

The reaction of the 16-electron “pseudo-aromatic” complex Cp*Ir[Se₂C₂(B₁₀H₁₀)] (1, Cp* = η⁵-C₅Me₅) with [Ir(cod)(µ-OC₂H₅)]₂ leads to the trinuclear iridium complexes {(cod)Ir[Se₂C₂(B₁₀H₈)(OC₂H₅)]}Ir{[Se₂C₂(B₁₀H₁₀)]IrCp*} (2), {(cod)Ir[Se₂C₂(B₁₀H₈)(OC₂H₅)]}Ir{[Se₂C₂(B₁₀H₉)]IrCp*} (3), {Cp*Ir[Se₂C₂(B₁₀H₉)]}{IrSe₂[C₂(B₁₀H₉)(OC₂H₅)]}{[Se₂C₂(B₁₀H₁₀)] IrCp*} (4) and one mononuclear complex Cp*Ir[Se₂C₂(B₁₀H₈)(OC₂H₅)₂] (5). The reactivity of 2 was investigated and revealed that transformation from 2 to 3 occurred thermally in solution. The transoid complex 2 (with the carborane diselenolato units in trans position) can be converted in nearly 90% yield to the cisoid complex 3. In complexes 2, 3, two diselenolato carborane ligands bridge the Ir₃ core, which consists of Ir–Ir metal bonds. Compared with transoid 2, the cisoid 3 contains two iridium–boron bonds. Complex 4 consists of three different coordination environment carborane ligands (Ir–B_cluster: {Cp*Ir[Se₂C₂(B₁₀H₉)]}, O–B_cluster: {[Se₂C₂(B₁₀H₉)](OC₂H₅)}, and intact carborane: {Cp*Ir[Se₂C₂ (B₁₀H₁₀)]}) without the presence of a metal–metal bond. Analogous reaction of 1 with [Ir(cod)(µ-OCH₃)]₂ results in formation of the trinuclear complex {Cp*Ir[Se₂C₂(B₁₀H₉)]}{IrSe₂[C₂(B₁₀H₉)(OCH₃)]}{[Se₂C₂(B₁₀H₁₀)]IrCp*} (6) and mononuclear complex Cp*Ir[Se₂C₂(B₁₀H₈)(OCH₃)₂] (7). The structures of 2, 3, 4, 5, 6 and 7 have been determined by crystallographic studies.