Covalent Bonding Between Ir and High-Oxidation State Sb Constrained by Quinoline Scaffolds

From the reaction of a high-valent Sb(V) proligand with a low-valent Ir(I) precursor in acetonitrile, a bimetallic Sb-Ir complex was isolated in which one of the quinoline groups inverted such that it is N-coordinated to Sb and C-coordinated to Ir. The new Sb-Ir complex has a unique structure containing the shortest reported Sb-Ir bond (2.51502(18) Å). Our combined experimental and computational studies indicate pronounced covalent character for the Sb-Ir bond. Based on the covalent bonding, the complex more closely resembles Sb(IV)-Ir(II) species rather than Sb(V)-Ir(I) and thus results in an Ir center with poor π-basicity, particularly toward the position trans to Sb.