An exploration of the structural and bonding variability in mixed-ligand benzimidazole-2-thione(bromo)(triarylphosphane)dicopper(I) complexes with diamond-shaped Cu-2(mu-X)(2) core structures

摘要

Reaction of copper(I) bromide with benz-1,3-imidazole-2-thione (bzimtH(2)) 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(bzimtH(2))(PR3)](2). The new complexes were characterized by IR, UV/Vis, and H-1 NMR spectroscopy, while the crystal structures of [{CuBr(mu(2)-S-bzimtH(2))(PPh3)}(2)](0.78)[{Cu(mu 2-Br)(PPh3)(bzimtH(2))}(2)](0.22) (1), [CuBr(mu(2)-S-bzimtH(2))(tptp)](2) (2) and [CuBr(mu(2)-S-bzimtH(2))(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(bzimtH(2))(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 Cu-I ions. The second one (molecule B) is disordered and can be resolved into two separate entities, one mu(2)-S dicopper(I) complex, similar to molecule A (molecule B1), and another one (molecule B2) involving mu(2)-Br bridges. In contrast, in complexes 2 and 3, with spectator tmtp and tptp ligands, only the bzimtH(2)-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" Cu-2(mu-X)(2) (X = S or Br) core structures and account well for their structural preferences. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).