Pyridine Complexes Help Expand Silicon Chemistry

A novel family of six-coordinate silicon-pyridine complexes promises to ease the costs of preparation and to improve control of compounds such as silane (SiH₄) that are used in key industrial processes involving high-purity silicon deposition, such as solar-cell fabrication (J. Am. Chem. Soc., DOI:10.1021/ja901053w). Edwin Kroke, Gerrit W. Fester, and colleagues of the Technical University Bergakademie, in Freiberg, Germany, synthesized the octahedral adducts in better than 95% yield by treating trichlorosilane or methyldichlorosilane with substituted pyridines at low temperature. The researchers also found that the trichlorosilane complexes are surprisingly stable and undergo hydrogen-chlorine exchange reactions under controlled conditions, forming products such as SiH₄. Although a few six-coordinate trichlorosilane-pyridine adducts have been synthesized before, the six-coordinate methyldichlorosilane adducts are new. Besides producing solar-cell-grade silicon, the compounds provide a basis for better control of many reactions of hydridochlorosilanes, including chlorine substitution and hydrosilylation, that are catalyzed by pyridine bases, the researchers say.