The catalytic activity in amine-borane dehydrogenation is shown for the first time for Ln(II) species using complexes [{(Bu-CH)CH}M·L] (M = Yb, Sm, L = (DME), TMEDA). The protonation of M(II)-C bonds with HNRRBH affords amidoborane complexes [M(NRRBH)L], which under excess HNMeBH transform to [NMeBHNMeBH] derivatives, both serving as the dehydrocoupling intermediates.
Ammonia boranes and amine boranes are main group analogues of alkanes, which are characterised by their large gravimetric hydrogen content. This hydrogen can be released in dehydrocoupling and dehydropolymerisation reactions to obtain B-N oligomers and polymers that are of importance as precursors for functional B-N materials. Furthermore, amine boranes are potent reagents for application in transfer hydrogenation reactions, representing a versatile, easy-to-handle alternative to the use of gaseous hydrogen for the reduction of organic compounds.
Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR), Universidad de Alcalá, 28805 Alcalá de Henares, Madrid, Spain.
Half-sandwich zirconium(IV) and hafnium(IV) complexes with amidoborane and hydride ligands have been isolated in the stoichiometric reactions of mono(pentamethylcyclopentadienyl)metal alkyl and amido derivatives with the amine-boranes NHRBH (R = H, Me, HBu). Treatment of the tris(trimethylsilylmethyl) complexes [M(η-CMe)(CHSiMe)] with NHBH (3 equiv) gives the seven-coordinate species [M(η-CMe)(NHBH)] (M = Zr (), Hf ()) with three κ-NHBH ligands. The tris(neophyl) [M(η-CMe)(CHCMePh)] or tris(dimethylamido) [M(η-CMe)(NMe)] derivatives react with NHMeBH (≥3 equiv) to afford bis(dimethylamidoborane) hydride complexes [M(η-CMe)H(NMeBH)] (M = Zr (), Hf ()) via thermally unstable [M(η-CMe)(NMeBH)] species.
Univ Lyon, Université Claude Bernard Lyon 1, CNRS, CNES, ArianeGroup, LHCEP, UMR 5278, Bât. Raulin, 2 rue Victor Grignard, 69622, Villeurbanne, France.
Amine-borane dimers and oligomers with varied steric and electronic profiles were prepared via capping agent-controlled AA/BB polycondensations. They were used for transfer hydrogenations to aldehydes, ketones, imines as well as electron-poor alkene/alkyne moieties. The amine-borane Lewis-paired oligomers and the congested bis(amine-borane)s provided the highest yields.
Tertiary amines are ubiquitous and play an essential role in organocatalysis, pharmaceuticals, and fine chemicals. Amongst various synthetic procedures known for their synthesis, the reductive amination of carbonyl compounds has been found to be a proficient method. Over the past few decades, different synthetic strategies for reductive amination have been developed.
Dehydrogenative borylation of terminal alkynes has recently emerged as an atom-economical one-step alternative to traditional alkyne borylation methodologies. Using lithium aminoborohydrides, formed in situ from the corresponding amine-boranes and -butyllithium, a variety of aromatic and aliphatic terminal alkyne substrates were successfully borylated in high yield. The potential to form mono-, di-, and tri--alkynylated products has been shown, though the mono-product is primarily generated using the presented condition.
