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

Density functional theory (DFT) and ab initio MP2 methods have been applied to characterize the structural features of seven different bonding isomers of copper() thiocyanate dianion complexes (Sand/or N-bonded). The DFT calculations were carried out by means of the hybrid Becke 3LYP functional, using the 6-3111G* basis set. The ab initio calculations were done at the MP2/6-3111G* 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() cation and the donor atoms is strongly polarized, almost ionic. The charge depletion around the copper() cation is in accordance with sp hybridization. Moreover, the canonical form for the non-co-ordinated as well as S-co-ordinated thiocyanates is mainly S–C]]N, whereas the N-bonded thiocyanates have also N]]C]]S contribution.