Kinetic and Mechanistic Studies of Highly Reactive Species Containing Electron-Deficient Main Group Atoms, and the Synthesis of Novel Molecules

Washington University, Saint Louis MO

Investigators

Abstract

The goal of this project is to understand the factors that control the reactions of electron-deficient and multiply bonded species containing second-, third- and fourth-row elements of groups 13, 14, and 15. The generation of dimethyldisilyne (MeSiSiMe) will be explored in order to address the structure and reactivity of molecules containing the silicon-silicon triple bond, as yet unknown. A novel class of electron-deficient species containing four valence electrons at the reactive atom, both charged (e.g. Br-C:+ and Ph-Si:+) and neutral (Ph-B: and Ph-Al:), offer the capability of forming three new bonds in either a concerted or stepwise manner. New precursors for reactive stannylenes (R2Sn:) will allow the exploration of the full range of reactions available to neutral molecules containing divalent tin atoms, without the presence of sterically shielding substituents. Sterically unencumbered lithiosilylenes R(Li)Si: will be used for the exploration of the chemistry of triplet silylenes, and a new program will be initiated for the design and construction of "molecular vices" that are rigid scaffolds capable of imposing preselected large bond angles on divalent species mounted between the jaws. This will allow the study of the spectroscopy and chemistry of molecules in unusual electronic states like triplet silylenes. The study of reactive carbon-based intermediates has shed light on the fundamental mechanisms by which organic reactions occur, providing both basic understanding and predictive tools for the control of organic reactivity. With the support of the Organic and Macromolecular Chemistry Program, Professor Peter P. Gaspar, of the Department of Chemistry at Washington University, is studying the preparation and reactivity of analogous species based on the heavier elements in the carbon group - silicon, germanium, and tin. These studies will lead to the extension of the powerful mechanistic ideas of organic chemistry to the prediction and rationalization of bond-making and bond-breaking processes throughout the periodic table, and in addition will provide predictive insights into the factors controlling the reactions involved in the chemical vapor deposition of silicon films that form the basis of much of the modern semiconductor industry.