Organotin isothiocyanate complexes: the interaction of alkyltin isothiocyanates with ligands containing oxygen or nitrogen as the donor atom

Abstract

Methyltin tri-isothiocyanate MeSn(NCS)₃ and the dialkyltin di-isothiocyanates R₂Sn(NCS)₂(R = Me, Et, Bu, and octyl) form six-co-ordinate adducts with some or all of the ligands pyridine, 1,10-phenanthroline, 2,2′-bipyridyl, pyridine 1-oxide, quinoline 1-oxide, triphenylphosphine oxide and triphenylarsine oxide. The stability of the complexes diminishes as the size of the alkyl group R is increased. The methyl groups occupy trans-positions in the octahedral Me₂Sn(NCS)₂ complexes. Trimethyltin isothiocyanate Me₃Sn(NCS) forms 1 : 1 adducts with monodentate ligands, the five-co-ordinate compounds having trigonal-bipyramidal structures with the methyl groups approximately in a plane around the tin atom. 1,10-Phenanthroline yields a six-co-ordinate complex Me₃Sn(NCS),phen, but 2,2′-bipyridyl behaves as a nonchelate ligand forming complexes Me₃SnNCS, bipy and 2Me₂SnNCS,bipy for which five-co-ordinate structures are proposed. Comparison with Me₃SnCl,bipy suggests that in this latter compound the bipyridyl is chelated and the tin atom six-co-ordinate.