Molecular modelling for coordination compounds:Cu(II)-aimne complexes

摘要

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 A 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 CuN_4 and tetragonally elongated CuN_6 complexes.In agreement with experiment,square-pyramidal coordination is marginally favoured over trigonal bipyramidal coordination for CuN_5 species.However,if the ligand requirements dictate,the LFMM accommodates trigonal bipyramidal coordination for CuN_5 species,tetrahedral distortions of CuN_4 species and cis-elongated CuN_6 species.