Theoretical investigation of the N → Sn coordination in (Me3SnCN)2

Abstract

The N → Sn coordination occurring in the (Me3SnCN)2 dimer has been investigated using various computational methods and several theoretical tools possessing great interpretative potential. The dimer is formed by moving the C=N fragment of the first Me3SnCN molecule close to the Sn atom of the second molecule and the resulting N → Sn coordination corresponds to that observed in the crystal structure of trimethyltin cyanide. The geometry of (Me3SnCN)2 is optimized using the MP2 method and its 11 variants, and then it is compared with the reference geometry obtained at the CCSD level of theory. SCS-MP2 reproduces best the reference geometry of (Me3SnCN)2 and its accuracy is close to that of the MP4(SDQ) method. Two families of basis sets, namely the correlation-consistent basis sets proposed by Dunning and co-workers and the 'def2' basis sets developed by Ahlrichs and co-workers, are taken into account and their effect on the geometry of the dimer is examined in detail. The intermolecular interaction in (Me3SnCN)2 has been analyzed using SAPT, NBO, QTAIM, and ELF. The results indicate that the (Me3SnCN)2 dimer possesses a weak N → Sn coordination bond whose character is predominantly ionic. A value of -7.64 kcal/mol is proposed to be the best estimate of the interaction energy between the Me3SnCN molecules in the dimer.