Dehydrogenation of dimethylamine-borane mediated by Group 1 pincer complexes

Abstract

Group 1 salts containing carbazolido NNN pincer ligands are precatalysts for the dehydrogenation of MeNH·BH. NMR monitoring and DOSY studies show a heavy dependence on the metal and solvent, allowing in some cases selective formation of dehydrogenation products consistent with hydrogen liberation.

Crystal structure of 4-bromo-N-[(3,6-di-tert-butyl-9H-carbazol-1-yl)methylidene]aniline

“…The dihedral angle between the mean planes of the carbazole ring system and the benzene C25-C30 ring is 42.72 (7) . The bond lengths and angles of the title compound are normal and agree with those values in other carbazole imine compounds (Gibson et al, 2003;Nolla-Saltiel et al, 2018). One of the tertbutyl substituents shows rotational disorder around the C13-C20 bond axis over two sites with occupancies of 0.592 (3) and 0.408 (3).…”

A Highly Active Bidentate Magnesium Catalyst for Amine‐Borane Dehydrocoupling: Kinetic and Mechanistic Studies

“…[34] However,r ecent work is yielding more active systems. [35,36] WhilstG roup 2s ystems have shown greater activityt owards morec omplex amineborane substrates, [37][38][39] it should be noted that some systems studied have subsequently been shown to exhibit "spontaneous" dehydrocoupling. [40] In contrast, the Me 2 NH·BH 3 and iPr 2 NH·BH 3 substrates investigated here showed no hydrogen releaseint he absence of catalyst.…”

“…Predominantly investigated as storage materials rather than catalysts, their lack of popularity may be due to poor selectivity and extended reaction times of, for example, 124 h (72 % conversion) with Me 2 NH⋅BH 3 as a substrate, as reported for Group 1 bis‐ (trimethylsilyl)amides . However, recent work is yielding more active systems . Whilst Group 2 systems have shown greater activity towards more complex amine‐borane substrates, it should be noted that some systems studied have subsequently been shown to exhibit “spontaneous” dehydrocoupling .…”

Bis(imino)carbazolate: A Master Key for Barium Chemistry

“…[25] The 19 Figure S22) revealed ad istorted tetrahedral geometry around potassium, with K-N interatomic distances [2.6479(11)-2.7332 (11) ]within the known ranges for potassium diiminocarbazolates. [38] (Figure 4). Thesix-coordinate metal centre rests in ad istorted anti-prismatic geometry.T he three Ba-N interatomic distances are fairly comparable,int he range 2.726(2)-2.801(2) ,a nd commensurate with those in 1.T he BaÀI bond length, 3.4052(3) ,m atches that for reported barium iodides.…”