Triangular tricopper(i) clusters supported by donor-substituted triazacyclohexanes

Abstract

Triazacyclohexanes (R₃TAC, 1a–i) with pyridyl or thioether functionalities (R) in the N-substituents react with three equivalents of CuX (X = Cl (2), Br (3) or I (4)) in MeCN to give the triangular tri-copper clusters [R₃TAC(CuX)₃] (R = 2-pyridylmethyl (2a, 3a), 5-^tbutyl-2-pyridyl (3b), 2-(3-phenylpropylthio)ethyl (3c), 2-(2-ethyl-butylthio)ethyl (3d), 2-(4-heptylthio)ethyl (2e, 3e), 2-(1-heptylthio)ethyl (3f), 2-(2,4,6-trimethyl-benzylthio)ethyl (3g), 2-(o-methyl-benzylthio)ethyl (3h) and 2-(o-fluoro-benzylthio)ethyl (2i, 3i, 4i)). The thioether complexes are stable towards air and water. The bromide bridge in the clusters can be replaced by chloride (2c, e, f, i) or iodide (4c, e, f, i) by the reaction of a dichloromethane solution of the cluster with aqueous NaI or AgCl, respectively. Crystal structures of 2a, 3a, 3b, 2e, 3h and 4i show triangular halide-bridged Cu₃ clusters capped by the triazacyclohexane and stabilised by the coordination of one pyridyl or thioether arm to each copper atom. DFT calculations confirm the NMR assignments and reveal the electronic structure of the copper triangle.