Electron spin resonance spectra and structure of the radical anions of methyl derivatives of halogeno-silanes and -germanes

Abstract

Monomethyl and dimethyl derivatives of halogeno-silanes and -germanes were exposed in tetramethylsilane matrices to γ-rays at 77 K and the radical anions formed from them were studied by e.s.r. spectroscopy. In accord with the results from a previous study on SiH3Br–, the radical anions of the derivatives of bromosilane were assigned trigonal bipyramid structures with a bromide atom and a hydrogen atom in the axial positions. However, a different conclusion was obtained for the radical anions of derivatives of iodosilane. Their structure may be better described as having local C3v symmetry at the central Si atom, in contrast to the trigonal bipyramidal structure of SiH3I–. On the other hand, radical anions formed from methyl derivatives of bromogermane and iodogermane were found to have local C3v symmetry at the central Ge atom, similar to that found for GeH3X–(X = Br or I). The structures of these radical anions are compared with one another and with those of ethyl radical–halide ion adducts produced in acetonitrile matrices.