Dinuclear copper complexes of pyridylphenylphosphine ligands: Characterization of a mixed-valence CuII/CuI dimer

Homo bi-copper complexes [cu(2){PhP(2-py)(2))(2)(NO3)(3)] (1) and [Cu-2{P(2-py)(3)}(2)Cl-2] (2), were synthesized from the reaction of Cu(NO3)(2)center dot 3H(2)O and CuCl2 center dot 2H(2)O with their corresponding 2-pyridylphosphine ligands. Compound 1 has a mixed valence Cu(I)-Cu(II) core with electron acceptor phosphine atoms and two NO3- anions coordinated in a monodentate fashion to Cu(I), giving it a distorted tetrahedral geometry. The environment of Cu(II) in 1 is composed of four nitrogen atoms from pyridyl and another NO3- anion in a square pyramidal geometry. This complex shows luminescence and a low energy absorption band at 969 nm corresponding to intermetallic electron transfer between the copper centers. Complex 2 was prepared from the treatment of copper(II) chloride with tris(2-pyridyl)phosphine, producing a binuclear copper complex which possesses a crystallographic inversion center. The copper geometry in this complex is distorted tetrahedral with coordination of one Cl-, two nitrogens from one bridging tris(2-pyridyl)phosphine ligand and one P atom from the other bridging tris(2-pyridyl)phosphine ligand, in a similar way observed in related complexes. The products have been characterized by spectroscopic methods and also by the single-crystal X-ray diffraction method. (C) 2011 Elsevier Ltd. All rights reserved.