Binuclear β-diketiminate complexes of copper(I)

The reaction of a series of dinucleating bis(beta-diketiminate) pro-ligands with mesitylcopper in the presence and absence of mono and diphosphines has allowed the isolation of a new series of dicopper(I) complexes. Inclusion of trans-1,2-cyclohexyl (1), 2,6-pyridyl (2), and 2,2'-oxydiaryl (3) spacers between the beta-diketiminate units has been studied. The isolation of three new copper(I) phosphine complexes [1 center dot Cu-2(PPh3)(2)], [2 center dot Cu-2(PPh3)(2)] and [3 center dot Cu-2(PPh3)(2)] is reported. While these compounds display large Cu center dot center dot center dot Cu separations of 5.4-7.9 angstrom in the solid state, solution data are consistent with a large degree of conformational freedom. Modification of the monophosphine to a diphosphine, DPPE, allowed the isolation of the novel 11-membered bimetallic macrocycle [2 center dot Cu-2(DPPE)] containing both a binucleating nitrogen based ligand and a chelating diphosphine. While acetonitrile adducts of this series could also be generated in situ, under forcing conditions reaction of the 2,6-pyridyl bridged ligand with mesityl copper led to the formation [2 center dot Cu-2](2). This latter complex is a dimer of dicopper(I) units in which the bis(beta-diketiminate) ligand now binds four copper(I) centers through not only the expected kappa(2)-N, N'-chelation but also kappa(1)-and eta(2)-binding of the central pyridine through orthogonal Cu-N and Cu-arene interactions. Reversible coordination of alkenes, pyridine and quinoline to the copper cluster was identified allowing the isolation and structural characterisation of a further series of dinuclear complexes [2 center dot Cu-2(pyridine)(2)], [2 center dot Cu-2(cyclopentene)(2)] and [2 center dot Cu-2(norbornene)(2)]. Solution studies allow quantification of the reversible binding event through a van't Hoff analysis. Both solution and the solid state data suggest a weak anagostic interaction exists in the latter two alkene complexes of copper(I). The new complexes have been characterized by X-ray diffraction, multinuclear NMR spectroscopy and CHN analysis.