Mono- and di-cationic hydrido boron compounds

Bronsted acid HNTf2 (Tf = SO2CF3) mediated dehydrogenative hydride abstraction from (L-1)BH3 (3) and (L-2)BH3 (4) (L-1 = IPrCH2 = 1,3-(2,6-di-isopropylphenyl) imidazol-2-methylidene (1); L-2 = SIPrCH2 = 1,3-(2,6-di-isopropylphenyl)imidazolidin-2-methylidiene (2)) affords thermally stable hydride bridged monocationic hydrido boron compounds [{(L-1)BH2}(2)(mu-H)](NTf2) (5) and [{(L-2)BH2}(2)(mu-H)](NTf2) (6). Furthermore, hydride abstraction yields di-cationic hydrido boron compounds [{(L-1) BH}(2)(mu-H)(2)](NTf2)(2) (7) and [{(L-2)-BH} 2(mu-H)(2)](NTf2)(2) (8). Unique cationic boron compounds with CH2BH2(mu-H)BH2CH2 (5 and 6) and CH2BH(mu-H)(2)BHCH2 (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.