Reactions of Hydridochlorosilanes with 2,2′-Bipyridine and 1,10-Phenanthroline: Complexation versus Dismutation and Metal-Catalyst-Free 1,4-Hydrosilylation

Abstract

Stable in the solid state and isolable in high yields are adducts of H(2)SiCl(2), HSiCl(3), and RSiCl(3) (R = Me, Ph) with the N,N'-chelating ligands 1,10-phenanthroline (phen; 1c), 2,2'-bipyridine (bipy; 1b), and (to a limited extent) N,N,N',N'-tetramethylethylenediamine (tmeda; 1a). The products were comprehensively characterized via multinuclear solution and solid-state NMR spectroscopy, including analysis of the (29)Si NMR chemical shift anisotropy tensors, Raman spectroscopy, elemental analyses, and, for SiCl(4)(phen) (2c), HSiCl(3)(bipy) (3b), H(2)SiCl(2)(bipy) (4b), MeSiCl(3)(phen) (5c), and PhSiCl(3)(phen) (6c), single-crystal X-ray structure analyses. The latter revealed that the nonchlorine substituents (i.e., H, Me, and Ph) are exclusively trans-disposed to the N-donor atoms of the chelating ligands. A dismutation of the complexes HXSiCl(2)(bipy) and HXSiCl(2)(tmeda) (X = H or Cl) was observed in polar solvents at elevated temperatures. This reaction is more pronounced when phen is used instead of bipy or tmeda. For MeHSiCl(2)(phen), in addition to undergoing H-Cl redistribution accompanied by the formation of 5c, an unexpected 1,4-hydrosilylation was observed. The latter was proven NMR-spectroscopically and by a single-crystal X-ray structure analysis of the product MeSiCl(2)(4H-phen) (7), a pentacoordinated silicon compound with a trigonal-bipyramidal arrangement of the subsituents and the methyl group located in an equatorial position.