On the bonding isomerism in three-co-ordinated copper(I) thiocyanates

Abstract

Density functional theory (DFT) and ab initio MP2 methods have been applied to characterize the structural features of seven different bonding isomers of copper(I) thiocyanate dianion complexes (S- and/or N-bonded). The DFT calculations were carried out by means of the hybrid Becke 3LYP functional, using the 6-311+G* basis set. The ab initio calculations were done at the MP2/6-311+G* theoretical level. The results indicate that in the gas phase N-bonding is preferred to S-bonding. The Atoms in Molecules theory was also employed to study the electronic properties in these isomers. The co-ordination bond between the copper(I) cation and the donor atoms is strongly polarized, almost ionic. The charge depletion around the copper(I) cation is in accordance with sp² hybridization. Moreover, the canonical form for the non-co-ordinated as well as S-co-ordinated thiocyanates is mainly ^–S–CN, whereas the N-bonded thiocyanates have also ^–NCS contribution.