Mono- and di-cationic hydrido boron compounds

Abstract

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

N‐Heterocyclic Vinylidene‐Stabilized Phosphorus Biradicaloid

“…All the P−C bond lengths (av 1.79 Å) are equal within three standard deviations, which are shorter than a P−C single bond but considerably longer than a P=C double bond length . The exocyclic C−C bond lengths (av 1.38 Å) are longer than the C=C bond length of 1 (1.332(4) Å) but shorter than the corresponding C−C bond length of 1 in donor–acceptor compounds (av 1.46 Å) . This indicates that a significant π‐electron density from the NHC has been transferred onto the C 2 P 2 ring, therefore 3 may also be regarded as a 6π‐electron aromate.…”

Cationic Complexes of Boron and Aluminum: An Early 21st Century Viewpoint

“…Ghadwal (Figure 14). [48] These are structurally related to Vedej's NHC complex 47 2 + ,b ut bulky NHO ligands differ in their electronic properties from NHCs. Both are comparably strong s-donors but NHOs possess only negligible p-accepting properties whereas NHCs are weak p acids.…”

“…[46] One should recognize that ac losely relatedc ompound using an NHO ligand was reported later by the group of Ghadwal (NHO = N-heterocyclic olefin). [48] Gessner and co-workers described the boron complex salt 29[PF 6 ]t hat bears two anionic carbon ylidic ligands and which was isolated and characterizedb yX RD analysis( Figure 9). [49] This ligand is marked by af ormally anionic carbon center with two lone pairs and, hence, it resembles an egatively charged version of the non-ionic carbone-typel igand mentioned above.The complex (29 + )w as accessed by hydride abstraction from the bisylide borane (Y 2 BH, Y = anionic ylide) using different salts of trityl cation with aW CA or using B(C 6 F 5 29[HB(C 6 F 5 ) 3 ]) formed highly viscous oils.…”

Single and Double Hydroboration of B–B Triple Bonds and Convergent Routes to a Cationic Tetraborane

“…5 Lewis base-stabilized dicationic, hydrogen bridged diboranes (F), formally dimers of borenium ions, have been reported by Curran and Vedejs 20 and Ghadwal. 21 A handful of neutral, base-stabilized dihydrodiboranes(4) (G) is known, [22][23][24][25][26] though this is likely to increase with the recent development of transfer hydrogenation to diborenes. 27 Very recently, the group of Yamashita reported the formation of a hydrogen-bridged tetraborane(6) (E, R = BR2) upon reductive coupling of the corresponding 1,1-dibromodiborane, presumably via radical hydrogen abstraction by a low-valent B4 intermediate.…”