Triorganotin Fluoride Structures: A Ligand Close‐Packing Model with Predominantly Ionic Sn−F Bonds

Abstract The synthesis and complete characterization by multinuclear NMR, infrared, and Mössbauer spectroscopy, by single crystal X‐ray analysis, as well as by electrospray mass spectrometry of the new soluble triorganotin fluoride Me 2 PhSnF ( 1 ) is reported. The crystal structure of 1 reveals a rod ‐ like polymeric structure in the solid state. Solutions of 1 in apolar solvents, such as toluene, contain mixtures of interconvertible oligomers. Ab initio MO calculations on model compounds H 3 SnF, [H 3 SnFSnH 3 ] + , and [FH 3 SnFSnH 3 F] − indicate that the Sn−F bonds are substantially ionic in character, and suggest open‐chain species, rather than cyclic species. In donor solvents, such as pyridine, 1 forms complexes with the solvent, such as Me 2 PhSnF·pyridine. The solid‐state structure of (Me 3 SiCH 2 ) 3 SnF ( 2 ) is reformulated as monomeric with a weak intermolecular Sn ··· F interaction that gives rise to a [4+1] coordination. The relative short Sn−Sn separation enables the fluorine atoms to oscillate (flip‐flop) between two neighboring (Me 3 SiCH 2 ) 3 Sn− groups, which is expressed in the X‐ray experiment by a dynamic disorder. Ab initio MO calculations on a model compound, [H 3 SnFSnH 3 ] + , suggest only a small energy barrier for the flip‐flop motion. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2003)