Lewis-Base Adducts of Group 11 Metal(I) Compounds. XLII. [Cu₄X₄L₄] 'Cubane' Clusters, L = Hindered N-Base Ligand: Synthesis and Structure of the L = 2-(Diphenylmethyl)pyridine Complexes (X = Cl, Br, I)

Abstract

The synthesis and single-crystal X-ray structure characterization of tetrameric cubane clusters of copper(1) halides with the hindered N-base ligand 2-(diphenylmethy1)pyridine are reported. The chloride, bromide and iodide structures are isomorphous , crystallizing in the tetragonal space group 14₁/a, a ≈ 23, c ≈ 12 Å , Z = 4 tetramers, the tetramer having crystallographically imposed 4 symmetry, well removed from the ideal 43m. In terms of each X₃CuN fragment of the core, this distortion results in one of the N-Cu-X angles being enlarged by c. 30º with respect to the other two and one Cu-X bond distance shortened. Cu-N is also shorter than is usual in a four-coordinate environment and the cluster can be envisaged as being constructed from four quasi-linear monomers. The distortions may be attributed to interaction between the 6- and 2-α-substituent-hydrogen atoms and the halide atoms of the core. The effect diminishes with increasing halide size and increasing volume of the Cu₄X₄ core.