Coordination Properties of N-Heterocyclic Stannylene with a Silane Bridge

Dimethylsilanediamine with mesityl substituents at the nitrogen atoms Me2Si(NHMes)2 was prepared by the direct reaction of Me2SiCl2 with mesitylamine, which acts as both reactant and base. Substitution of one chlorine atom by an amine residue to form chloroaminosilane Me2SiCl(NHMes) proceeds readily, while substitution of the second chlorine requires heating and removal of mesitylammonium chloride from the reaction mixture. The reaction of Me2Si(NHMes)2 with tin diamide Sn(NTms2)2 afforded a new N-heterocyclic stannylene, Me2Si(NMes)2Sn (SnMes), in high yield. Complexes of the stannylene as an Sn-donor ligand with several metals (Cr, Fe, Ni) in the zero oxidation state were obtained: [Ni(SnMes)4], [Fe(CO)4(µ-SnMes)]2, and mer-[Cr(CO)3(SnMes)3]. The crystal structures of the prepared compounds, as well as of the byproduct of stannylene oxidation by oxygen [Sn(Me2Si(NMes)2)2], were determined by X-ray diffraction analysis. The molecular structure of stannylene Me2Si(NMes)2Sn and its complexes as a ligand is compared with known analogous compounds containing a tert-butyl fragment at the nitrogen atoms. NMR and IR spectroscopy showed that the N-donor properties of Me2Si(NMes)2Sn are less pronounced than those of its analog with N-tBu substituents, while the Sn-donor properties, determined by the Tolman electronic parameter, are similar for both stannylenes and are comparable to arylphosphines.