Borenium Ion Equivalents Stabilized by BICAAC and Their Implementation as Catalysts in Hydrosilylation of Carbonyls.

Hydride abstraction from the borane adduct, (BICAAC) ⋅ BH3 afforded the hydride bridged dinuclear borenium ion equivalent complexes <bold>1</bold> and <bold>2</bold> that have been characterized by various spectroscopic and spectrometric techniques followed by the assessment of Lewis acidity using the Gutmann‐Beckett method. The single crystal X‐ray structure of complex <bold>2</bold> revealed the presence of discrete ions in the solid state. The complex (BICAAC) ⋅ BH2(OTf) (<bold>3</bold>), obtained from the reaction of (BICAAC) ⋅ BH3 with MeOTf, formed the corresponding boronium cations [(BICAAC) ⋅ BH2(L)]+(OTf)− on reaction with Lewis bases (L= pyridine (<bold>4</bold>) and DMAP (<bold>5</bold>)). Complexes <bold>1</bold> and <bold>2</bold> demonstrated notable catalytic activity in the hydrosilylation of a diverse array of carbonyls using 1.0 mol % catalyst loading (achieving the highest turnover frequency (TOFmax) of up to 1200 h−1 with benzaldehyde. A broad substrate scope has been presented for aldehydes and ketones decorated with various electron‐donating and withdrawing substituents along with this the hydrosilylation of a few <italic>para</italic>‐quinone methides has also been presented. [ABSTRACT FROM AUTHOR]