The gas-phase reactions of SiCl4 and Si2Cl6 with CH3OH and C2H5OH: An investigation by mass spectrometry and matrix-isolation infrared spectroscopy

Abstract

The gas phase reactions of SiCl₄ and Si₂Cl₆ with CH₃OH and C₂H₅OH have been investigated using both mass spectrometry and matrix isolation techniques. SiCl₄ reacts with both CH₃OH and C₂H₅OH upon mixing of the vapours for times in excess of 3 h to generate the HCl-elimination products SiCl₃OR (R = CH₃ or C₂H₅). The identity of these products is confirmed by deuteration experiments and by ab initio calculations at the HF/6-31G(d) level. Further products are generated when the mixture is passed through a tube heated to 750 °C. Si₂Cl₆ reacts with CH₃OH and C₂H₅OH via a different mechanism in which the Si–Si bond is cleaved to yield SiCl₃OR and HCl. Other products of the type SiCl_4−n(OCH₃)_n are tentatively identified by a combination of mass spectrometric and matrix isolation measurements. These latter products indicate further replacement of Cl atoms by OR groups as a result of reaction of CH₃OH or C₂H₅OH with the initial product.