Mono- and di-cationic hydrido boron compounds

Bronsted 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.