Molecular modelling for coordination compounds: Cu(ii)–amine complexes

Abstract

The Ligand Field Molecular Mechanics (LFMM) method has been applied to 85 Cu(II)–amine complexes, eighteen of which were selected to form a training set. A single set of parameters yields Cu–N bond lengths for four-, five- and six-coordinate systems generally within 0.04 Å of their X-ray crystallographic values. Larger deviations are indicative of counterion effects and/or crystallographic artefacts arising from Jahn–Teller averaging. The LFMM treatment is flexible and unbiased and for simple ligands, automatically gives planar CuN₄ and tetragonally elongated CuN₆ complexes. In agreement with experiment, square-pyramidal coordination is marginally favoured over trigonal bipyramidal coordination for CuN₅ species. However, if the ligand requirements dictate, the LFMM accommodates trigonal bipyramidal coordination for CuN₅ species, tetrahedral distortions of CuN₄ species and cis-elongated CuN₆ species.