Mono- and di-cationic hydrido boron compounds

Abstract

Brønsted acid HNTf₂ (Tf = SO₂CF₃) mediated dehydrogenative hydride abstraction from (L¹)BH₃ (3) and (L²)BH₃ (4) (L¹ = IPrCH₂ = 1,3-(2,6-di-isopropylphenyl)imidazol-2-methylidene (1); L² = SIPrCH₂ = 1,3-(2,6-di-isopropylphenyl)imidazolidin-2-methylidiene (2)) affords thermally stable hydride bridged mono-cationic hydrido boron compounds [{(L¹)BH₂}₂(μ-H)](NTf₂) (5) and [{(L²)BH₂}₂(μ-H)](NTf₂) (6). Furthermore, hydride abstraction yields di-cationic hydrido boron compounds [{(L¹)BH}₂(μ-H)₂](NTf₂)₂ (7) and [{(L²)BH}₂(μ-H)₂](NTf₂)₂ (8). Unique cationic boron compounds with CH₂BH₂(μ-H)BH₂CH₂ (5 and 6) and CH₂BH(μ-H)₂BHCH₂ (7 and 8) moieties feature a 3c–2e bond and have been fully characterized. Interesting electronic and structural features of compounds 5–8 are analysed using spectroscopic, crystallographic, and computational methods.