2-(Dimethylphosphinomethyl)- and 2-(methylthiomethyl)phenyl silicon compounds: higher coordination with soft donors

The synthesis of trimethoxy-, trifluoro-, trihydrido-, and hydrido(phenyl)chlorosilanes, and of hydrido(phenyl)silyltriflates bearing an additional 2-(dimethylphosphinomethyl)phenyl- or a 2-(methylthiomethyl)phenyl substituent is described. The coordination of the phosphorus and sulfur donor in the aryl side chain to the silicon center is discussed on the basis of NMR spectroscopic investigations. The trimethoxy and trifluorosilanes do not show any coordination. Weak donor–silicon interactions are found in the trihydrido- and in the hydrido(phenyl)chlorosilanes. The crystal structure of chloro-bis-[(2-(methylthiomethyl)phenyl]silane (13) [Angew. Chem. 111 (1999) 2071] features a distorted tetrahedral geometry at silicon with an additional weak donor-coordination. Different structural properties were found in the corresponding P- and S-donor functionalized phenylsilyl triflates. The S-donor compound 15 features a covalent structure with pentacoordination and a trigonal-bipyramidal geometry at the silicon atom. In the analogous P-donor derivative 14 the spectroscopic data indicate an ionic structure with a tetracoordinated silicon atom.