Silylenes: A Unified Picture of Their Stability, Acid−Base and Spin Properties, Nucleophilicity, and Electrophilicity via Computational and Conceptual Density Functional Theory

Conceptual DFT gives sharp definitions for many long-known, but rather vaguely defined chemical concepts. In this study DFT-based reactivity indices are applied to silylenes in order to elucidate the relationships among their properties: stability, acid-base, and spin properties, nucleophilicity and electrophilicity. On the basis of a detailed, comparative analysis of previously published data, it is shown that the properties of simple silylenes can be tuned by varying one single factor, the pi-electron donating ability of the substituents of the silicon atom leading to well-characterized and systematic changes in the stability/reactivity pattern of the molecule. In order to test the model a series of new compounds are studied: including CH3SiR (where R = CH3, NH2, OH and SH), Si(Si(CH3)3)2, Si(CF3)2 and benzo-, pyrido-, pyridazo-, and pyrimido-anellated-1,3,2lambda2-diazasiloles.