Strain-Modulated Reactivity: an Acidic Silane.

Strain-Modulated Reactivity: an Acidic Silane.
Angew Chem Int Ed Engl. 2021 Jan 21;:
Authors: Moret ME, Tretiakov S, Witteman L, Lutz M
Abstract
Compounds of main-group elements such as silicon are attractive candidates for green and inexpensive catalysts. For them to compete with state-of-the-art transition metal complexes, new reactivity modes must be unlocked and controlled, which can be achieved through strain. Using a tris(2-skatyl)methylphosphonium ([TSMPH 3 ] + ) scaffold, we prepared the strained cationic silane [TSMPSiH] + . In stark contrast with the generally hydridic Si-H bond character, it is acidic with an experimental pK a DMSO within 4.7-8.1, lower than in phenol, benzoic acid and the few hydrosilanes with reported pK a 's. We show that ring strain significantly contributes to this unusual acidity along with inductive and electrostatic effects. The conjugated base, TSMPSi, activates a THF molecule in the presence of CH-acids to generate a highly fluxional alkoxysilane via trace amounts of [TSMPSiH] + functioning as a strain-release Lewis acid. This reaction involves a formal oxidation state change from Si(II) to Si(IV), presenting intriguing similarities with transition metal-mediated processes.
PMID: 33476423 [PubMed - as supplied by publisher]

Source: Angewandte Chemie - January 21, 2021 Category: Chemistry Authors: Moret ME, Tretiakov S, Witteman L, Lutz M Tags: Angew Chem Int Ed Engl Source Type: research