A metallacyclic alkyl-amido carbene complex (MCAAC)??

摘要

The activation of the C≡N moiety in the redox-active metalloligand [CpRu{κ~3N_(pz)-1}][PF_6] (2) (1: ambidentate hybrid ligand, N≡C–C(pz)3, with pz = pyrazolyl) was observed in the reaction with [Ir(cod)Cl]_2 (cod = 1,5-cyclooctadiene). By performing detailed NMR spectroscopic and X-ray crystallographic investigations the product was found to be a bimetallic Ru~(II)–Ir~(III) complex of the composition [CpRu{μ-1’}Ir(cod)Cl_2][PF_6] (3) consisting of a chemically modified ligand 1’. Most notably, the heterobimetallic complex 3 features an unprecedented metallacyclic alkyl-amido carbene (MCAAC) core structure, which is coordinated to an Ir~(III) centre. Density functional theory (DFT) calculations as well as cyclic voltammetry (CV) studies were performed in an effort to establish the formal oxidation states of the metal atoms in 3. Indeed, a quasi-reversible oxidation wave was detected at E_(1/2)~0 = 0.36 V, which was attributed to the Ru~(II)/Ru~(III) redox couple, while two irreversible reduction processes were observed at very negative potentials and have been assigned to the stepwise reduction of Ir~(III) to Ir~I. First efforts to elucidate the reaction mechanism have also been performed.