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Past one decade has witnessed a tremendous growth in the field of carbene stabilized low-valent silicon compounds unravelling very exciting properties of these molecules. Herein, we have employed a bicyclic (alkyl)(amino)carbene, ( Me BICAAC) to explore the low-valent chemistry of silicon. The reduction of bicyclic (alkyl)(amino)carbene-SiCl 4 complex, [( Me BICAAC)SiCl 4 ] (1) with KC 8 afforded low-valent Si complexes, including Si(III) radical [( Me BICAAC)SiCl 3 ] (2) and a complex with silicon center in a formal zero-valent state, [( Me BICAAC) 2 Si] (3). Similarly, the reduction of in-situ generated Me BICAAC adduct of Me 2 SiCl 2 with one equivalent of KC 8 led to the formation of [( Me BICAAC)SiMe 2 Cl] (4) complex having an unpaired electron. These complexes have been characterized by IR, UV-Vis., NMR, HRMS, EPR and their solid-state structures were also elucidated by single crystal X-ray crystallography. Further, DFT calculations revealed the lower energy singlet state for complexes 1, 3 and doublet state for complexes 2, 4., (© 2024 Wiley-VCH GmbH.)

Hydride abstraction from the borane adduct, (BICAAC) ⋅ BH 3 afforded the hydride bridged dinuclear borenium ion equivalent complexes 1 and 2 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 2 revealed the presence of discrete ions in the solid state. The complex (BICAAC) ⋅ BH 2 (OTf) (3), obtained from the reaction of (BICAAC) ⋅ BH 3 with MeOTf, formed the corresponding boronium cations [(BICAAC) ⋅ BH 2 (L)] + (OTf) - on reaction with Lewis bases (L= pyridine (4) and DMAP (5)). Complexes 1 and 2 demonstrated notable catalytic activity in the hydrosilylation of a diverse array of carbonyls using 1.0 mol % catalyst loading (achieving the highest turnover frequency (TOF max ) 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 para-quinone methides has also been presented., (© 2024 Wiley-VCH GmbH.)