Expanding the family of C,N-chelated organotin(IV) pseudohalides: Synthesis and structural characterization

Abstract

A set of tri- and diorganotin(IV) pseudohalides bearing the 2-(N,N-dimethylaminomethyl)phenyl-as a C,N-chelating ligand (LCN) has been prepared and structurally characterized. Triorganotin(IV) pseudohalides of the type LCNR2SnX [R = n-Bu, X = NCO (1a), NCS (1b), NCSe (1c), CN (1d); R = Ph, X = NCO (2a), NCS (2b), NCSe (2c), CN (2d)] and (LCN)2(n-Bu)SnX [X = NCO (3a), NCS (3b), NCSe (3c), CN (3d)] are monomeric both in solution and the solid state. The central tin atom in these species is five-coordinated in the solid state with distorted trigonal bipyramidal geometry. Monomeric diorganotin(IV) pseudohalides of the type (LCN)2SnX2 [X = NCO (4a), NCS (4b), NCSe (4c), CN (4d)] contain six-coordinated tin atoms with heavily distorted octahedral geometry both in solution and solid state due to the presence of two LCN units. Finally, we have found that LCN(n-Bu)Sn(NCS)2 (5) is presumably dimeric in CDCl3 and monomeric in THF-d8 or DMSO-d6 solution while it forms infinite linear polymer in the solid state via thiocyanate bridges. According to IR, multinuclear NMR spectroscopy and XRD analysis, it was found that the pseudohalide ligands of the NCY type (Y=O, S, Se) are bound via nitrogen while the CN substituent act as a common cyanide ligand (i.e. binds via carbon). DFT calculations were performed for selected compounds (2a, 2b, 2d and 4d) to further support our conclusions about the nature of the Sn-pseudohalide bonds. Compound LCNSnPhI2 (6), which was prepared in the scope of this work as well has a trigonal bipyramidal structure with non-equivalent iodine atoms.