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Strain‐Modulated Reactivity: An Acidic Silane
Author(s) -
Tretiakov Serhii,
Witteman Léon,
Lutz Martin,
Moret MarcEtienne
Publication year - 2021
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202015960
Subject(s) - chemistry , reactivity (psychology) , silane , cationic polymerization , lewis acids and bases , transition metal , catalysis , metal , strain (injury) , silicon , polymer chemistry , organic chemistry , medicine , alternative medicine , pathology
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 p K a DMSO within 4.7–8.1, lower than in phenol, benzoic acid, and the few hydrosilanes with reported p K a values. We show that ring strain significantly contributes to this unusual acidity along with inductive and electrostatic effects. The conjugate 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.