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Contributions to the chemistry of halosilane adducts

1990; Elsevier BV; Volume: 382; Issue: 3 Linguagem: Inglês

10.1016/0022-328x(90)80212-i

1872-8561

D. Kummer, S. C. Chaudhry, J. Seifert, B. Deppisch, G. Mattern,

Inorganic Fluorides and Related Compounds

2,2′-Dipyridyltrimethylsilylamine reacts with chloro- and bromomethyl(methyl) chlorosilanes to give Si-functional 1-(2-pyridone-(2′-pyridyl)imine) methylsilanes. Their solid state and solution structures have been determined. Depending on the halogen and the number of halogen atoms neutral pentacoordinate Si-species, RN-2-(C5H4NCH2SiMexCl3−x) (R = 2-C5H4N; x = 1 (2); x = 0 (3)) or ionic tetracoordinate Si-species [R-N-2-(C5H4NCH2SiMe2)]+Br− (4) are obtained in solution and as solids. The solid compound with x = 2 (1) is also pentacoordinate at Si. In solution there is an interesting temperature-dependent equilibrium between the neutral pentacoordinate and the ionic tetracoordinate structure (at lower temperature, NMR) of 1. For the pentacoordinate species dissociation of the coordinative SiN bond and formation of the neutral tetravalent silanes is suggested at higher temperature in solution. The temperature-dependent equilibrium between the isomers of 1 thus follows reversibly the SN2 pathway of nucleophilic substitution at silicon. The solid state structures of 1 and 3 and of 1-methyl-2-(2′-pyridyl)aminopyridinium chloride (5) are discussed. Structural differences between solid 1 and 3 are interpreted in terms of different stages of the SN2 reaction at silicon.