23884-11-9Relevant articles and documents
Mechanistic insights into dehydrocoupling of amine boranes using dinuclear zirconocene complexes
Al Hamwi, Hanan,Beweries, Torsten,Drexler, Hans-Joachim,Heller, Detlef,Jannsen, Nora,Lindenau, Kevin,Neymeyr, Klaus,Rei?, Fabian,Rippke, Mirko,Sawall, Mathias,Selle, Carmen,Spannenberg, Anke
supporting information, p. 4034 - 4050 (2021/07/06)
Catalytic dehydrocoupling of H3B·NMe2H using the in situ system Cp2Zr(Cl)(μ-Me3SiC3SiMe3)Zr(Cl)Cp2 (1)/MeLi was studied as a model for previously reported dehydropolymerisation of H3B·NMeH2. NMR and UV-vis spectroscopic monitoring of the precatalyst activation sequence as well as a series of stoichiometric experiments showed that formation of a zirconocene dimethyl complex (2) is not relevant for activation of the precatalyst. Instead, deprotonation of H3B·NMe2H and reaction of thus formed Li[NMe2BH3] is proposed to result in the formation of Zr amidoborane and hydride species. DFT analysis using such complexes as active species showed a pathway for formation of H2 and H2BNMe2. 1H NMR spectroscopic monitoring and stoichiometric control experiments revealed the formation of unusual diamagnetic dinuclear complexes Cp2Zr(C2SiMe3)(μ-R)ZrCp2 (R = CH2SiMe3, 7; R = H, 9) formed by activation of the allenediide unit of the precatalyst 1. Such species can be regarded as rare single-component catalysts for the dehydrocoupling of amine boranes. This journal is
Dehydropolymerisation of Methylamine Borane and an N-Substituted Primary Amine Borane Using a PNP Fe Catalyst
Anke, Felix,Boye, Susanne,Spannenberg, Anke,Lederer, Albena,Heller, Detlef,Beweries, Torsten
supporting information, p. 7889 - 7899 (2020/06/02)
Dehydropolymerisation of methylamine borane (H3B?NMeH2) using the well-known iron amido complex [(PNP)Fe(H)(CO)] (PNP=N(CH2CH2PiPr2)2) (1) gives poly(aminoborane)s by a chain-growth mechanism. In toluene, rapid dehydrogenation of H3B?NMeH2 following first-order behaviour as a limiting case of a more general underlying Michaelis–Menten kinetics is observed, forming aminoborane H2B=NMeH, which selectively couples to give high-molecular-weight poly(aminoborane)s (H2BNMeH)n and only traces of borazine (HBNMe)3 by depolymerisation after full conversion. Based on a series of comparative experiments using structurally related Fe catalysts and dimethylamine borane (H3B?NMe2H) polymer formation is proposed to occur by nucleophilic chain growth as reported earlier computationally and experimentally. A silyl functionalised primary borane H3B?N(CH2SiMe3)H2 was studied in homo- and co-dehydropolymerisation reactions to give the first examples for Si containing poly(aminoborane)s.
Stable BH3adducts to rhodium amide bonds
Müller, Fabian,Trincado, Monica,Pribanic, Bruno,Vogt, Matthias,Grützmacher, Hansj?rg
, p. 154 - 162 (2016/11/01)
Rh(I) diolefin amides, [Rh(trop2N)(L)] (trop2N?=?bis(5H-dibenzo[a,d]cyclohepten-5-yl)amide), form the corresponding hydrido amine species, [RhH(trop2NH)(L)], by reaction with Me2HN-BH3(DMAB). Both amide and amine complexes are active dehydrocoupling catalysts, forming the monomer [Me2N?=?BH2], the linear [Me2NHBH2NMe2BH3] and the cyclic dimer [Me2BNH2]2. Good catalytic activity was observed especially for complexes which contain a metal hydride unit, Rh–H, in a co-planar cis-arrangement with respect to the N-H unit and for those bearing an N-heterocyclic carbene ligand (IMe) in trans-position to the active basic site of the ligand. Four-membered Rh–N–B–H metallacycles [Rh{(μ-H)BH2}(Ntrop2)(L)] (L?=?PPh3, IMe) were isolated by direct reaction of the amide complex with BH3(THF). These stable species are not active in the dehydrogenation of DMAB. Their isolation and lack of reactivity gives some indication for a possible catalyst deactivation. This observation is consistent with a mechanism in which the unprotected amine or amide ligand is essential for N–H and B–H bond cleavage.
