Synthesis and structure of di- and tetra-copper(I) complexes bridged by pyridazine

Abstract

Novel di- and tetra-copper(I) complexes of pyridazine (pydz) have been prepared and determined crystallographically. The yellow crystals of the dicopper(I) complex, [Cu₂(pydz)₃(MeCN)₂][PF₆]₂1 are monoclinic, space group C2/c, with a= 21.720(6), b= 8.803(8), c= 15.778(6)Å, β= 114.33(2)°, Z= 4, R= 0.056 and R′= 0.072. Two copper atoms are triply bridged by three pydz ligands to give a binuclear structure, in which the Cu ⋯ Cu separation is 3.065(2)Å. Each Cu atom is co-ordinated by three N atoms of three pydz molecules and one N atom of a MeCN molecule, providing a distorted tetrahedral environment. The orange crystals of the tetracopper(I) complex, [Cu₄(pydz)₆][ClO₄]₄·2Me₂CO 2 are monoclinic, space group P2₁/a, with a= 16.368(2), b= 13.860(2), c= 10.542(2)Å, β= 102.25(1)°Z= 2, R= 0.050 and R′= 0.058. Two Cu atoms are bridged by four N atoms of two pydz molecules to form a six-membered N₂Cu₂N₂ framework. Furthermore, two parallel N₂Cu₂N₂ frameworks are linked by two different pydz molecules to give a tetranuclear structure. Four Cu atoms are coplanar and each Cu atom is in a trigonal–square environment. The shortest Cu ⋯ Cu separations are 3.096(1) and 3.264(1)Å. If in the preparation of 2 ethylene or CO atmospheres are employed instead of Ar, copper(I) pydz adducts with C₂H₄ or CO are obtained which have been characterized by IR and ¹H NMR spectroscopy. The former shows v_CC of C₂H₄ at 1541 cm^–1; the latter shows ν_co at 2108 cm^–1.