Dicopper(I) complexes containing intramolecular 1,2-diaza bridging ligands. Behaviour of the dicopper site in the dehydrogenation of hydrazobenzene. Crystal structure of [Cu2L2(pydz)2][ClO4]2

Abstract

Dicopper(I) complexes of two 20-membered N₄ macrocycles and incorporating exogenous 1,2-diaza bridging ligands have been prepared. An X-ray crystallographic structure determination of the complex [Cu₂L²(pydz)₂][ClO₄]₂(pydz = pyridazine, L²= 5,5,16,16-tetramethyl-23,24-dioxa-3,7,14,18-tetra-azatricyclo[18.2.1.1^9,12]tetracosa-2,7,9,11,13,18,20,22-octaene) has been carried out. Crystals are monoclinic, space group P2₁/c with a= 9.71(1), b= 15.64(2), c= 12.52(1)Å, β= 105.5(1)°, and Z= 2. In the centrosymmetric cation the copper atoms have a distorted tetrahedral environment, being bonded to two nitrogens of the macrocycle [2.010(13), 2.044(11)Å] and to the nitrogen atoms of the bridging pydz molecules [1.938(14), 2.116(14)Å]. The Cu ⋯ Cu distance is 3.150(5)Å. Dicopper complexes of L² catalyse the dehydrogenation of hydrazobenzene to trans-azobenzene in cleaner and more quantitative fashion but at a slower rate than free Cu^I ions.