Synthesis and 1H NMR studies of some pentacoordinate tin(IV) complexes derived from triphenyltin halides

Abstract

Several anionic—cationic and neutral pentacoordinate tin(IV) complexes were prepared by the reaction of triorganotin(IV) halides, R 3SnX (R =Me and X =Cl; R =Ph and X =F, Cl, Br) with tetraalkylammonium halides and neutral ligands (pyridine, 4-(dimethylamino)pyridine, hexamethylphosphoramide and triphenylphosphine oxide). The complexes were examined in solution by 1H NMR spectroscopy and characterized as having trigonal bipyramidal geometry around tin where the phenyl groups occupy the equatorial sites and more electronegative ligands are at axial positions. The 1H NMR spectra of these complexes showed two distinct sets of aromatic multiplets arising from ortho-protons at low field, and meta- and para-protons at high field. A possible rationale has been offered for this observation. The upward shift of the tetraalkylammonium proton resonances in the phenyl-substituted complexes has been postulated to arise from shielding caused by the aromatic ring.