Understanding the stability, electronic and molecular structure of some copper(III) complexes containing alkyl and non alkyl ligands: Insights from DFT calculations

DFT calculations have been performed for some Cu(III)-alkyl complexes. Complexes 1-19 were optimized to the square planar (sq) geometry and observed no imaginary frequencies. Although formally copper adopts d(8) configuration (Cu(III)) in all the complexes, the Natural Population Analysis (NPA) revealed that the copper actually in d(10) (Cu(I)) configuration, Bond order calculation suggested that the Cu(III)-Et-trans bond gets more bond order in the presence of poor pi-acidic co-ligand (probe ligand). Relatively smaller bond order was calculated for Cu(III)-Me-cis bond than Cu(III)-Et-trans bond and therefore Cu(III)-Et-trans bond is the strongest bond in all the complexes. Calculated less Chemical hardness (eta) of complexes 1-19 suggested that all these complexes are less stable in nature. Energy Decomposition Analysis (EDA) revealed that the Cu(III)-Et-trans bond is relatively more stable than the Cu(III)-Me-cis and Cu(III)-L (L = co-ligand/probe ligand) bonds. And also the Cu(III)-alkyl (Cu(III)-Me-cis and Cu(III)-Et-trans) bond in complexes 1-17 is more of ionic in nature. However, Cu(III)-Et-trans bond is relatively more ionic than Cu(III)-Me-cis bond. (C) 2011 Elsevier B.V. All rights reserved.