An Exploration of the Structural and Bonding Variability in Mixed‐Ligand Benzimidazole‐2‐thione(bromo)(triarylphosphane)dicopper(I) Complexes with Diamond‐Shaped Cu2(μ‐X)2 Core Structures

Abstract

AbstractReaction of copper(I) bromide with benz‐1,3‐imidazole‐2‐thione (bzimtH2) in the presence of one equivalent of triphenylphosphane (PPh3), tri‐meta‐tolylphosphane (tmtp) or tri‐para‐tolylphosphane (tptp) in acetonitrile/methanol solvent afforded dinuclear complexes formulated as [CuBr(bzimtH2)(PR3)]2. The new complexes were characterized by IR, UV/Vis, and 1H NMR spectroscopy, while the crystal structures of [{CuBr(μ2‐S‐bzimtH2)(PPh3)}2]0.78[{Cu(μ2‐Br)(PPh3)(bzimtH2)}2]0.22 (1), [CuBr(μ2‐S‐bzimtH2)(tmtp)]2 (2) and [CuBr(μ2‐S‐bzimtH2)(tptp)]2 (3) were determined by single‐crystal X‐ray diffraction methods. In complex 1, with spectator PPh3 ligands, the unit cell of the crystal consists of two different half‐molecules, both corresponding to the formula [CuBr(bzimtH2)(PPh3)]2. One of the two molecules (molecule A) is a symmetrical dicopper(I) complex in which the exocyclic thione S‐atoms serve as bridges between the CuI ions. The second one (molecule B) is disordered and can be resolved into two separate entities, one μ2‐S dicopper(I) complex, similar to molecule A (molecule B1), and another one (molecule B2) involving μ2‐Br bridges. In contrast, in complexes 2 and 3, with spectator tmtp and tptp ligands, only the bzimtH2‐bridged dicopper complexes are formed. Density functional calculations at the B3LYP level of theory provided a satisfactory description of the structural, bonding, electronic and related properties of all dicopper complexes exhibiting the “diamond‐shaped” Cu2(μ‐X)2 (X = S or Br) core structures and account well for their structural preferences. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)