2386-98-3Relevant articles and documents
Preparation of trialuminum triboron heptakis(dimethylamino)pentahydride
Hall,Schram
, p. 270 - 274 (1969)
Treatment of bis(trimethylamine)-alane, [(CH3)3N]2AlH3, with tetrakis(dimethylamino)diborane(4), [(CH3)2N]4B2, results in the formation of the following known compounds: H2, (CH3)3N, [(CH3)2NBH2]2, [(CH3)2N]2BH, and (CH3)3NBH3. In addition, a new species was prepared, Al3B3[N(CH3)2]7H 5, which most likely contains three B-Al bonds. Characterization of this new compound is discussed.
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.
Catalytic Dehydrocoupling of Amine-Boranes using Cationic Zirconium(IV)-Phosphine Frustrated Lewis Pairs
Metters, Owen J.,Flynn, Stephanie R.,Dowds, Christiana K.,Sparkes, Hazel A.,Manners, Ian,Wass, Duncan F.
, p. 6601 - 6611 (2016/10/14)
A series of novel, intramolecular Zr(IV)/P frustrated Lewis pairs (FLPs) based on cationic zirconocene fragments with a variety of ancillary cyclopentadienyl and 2-phosphinoaryloxide (-O(C6H4)PR2, R = tBu and 3,5-CF3-(C6H3)) ligands are reported and their activity as catalysts for the dehydrocoupling of dimethylamine-borane (Me2NH·BH3) assessed. The FLP system [(C9H7)2ZrO(C6H4)PtBu2][B(C6F5)4] is shown to give unprecedented turnover frequencies (TOF) for a catalyst based on a group 4 metal (TOF ≥ 600 h-1), while also proving to be the most efficient FLP catalyst reported to date. The mechanism of this reaction has been probed using analogous intermolecular Zr(IV)/P FLPs, permitting deconvolution of the reactions taking place at both the Lewis acidic and basic sites. Elucidation of this mechanism revealed an interesting cooperative two-cycle process where one cycle is FLP mediated and the other, a redistribution of a linear diborazane intermediate, relies solely on the presence of a Zr(IV) Lewis acid.
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.
Titanocene(iii) complexes with 2-phosphinoaryloxide ligands for the catalytic dehydrogenation of dimethylamine borane
Klahn, Marcus,Hollmann, Dirk,Spannenberg, Anke,Brückner, Angelika,Beweries, Torsten
, p. 12103 - 12111 (2016/01/15)
A study of the dehydrogenation of dimethylamine borane using different titanocene(iii) complexes with 2-phosphinoaryloxide ligands is presented. Complexes Cp2Ti(κ2-O, P-O-C6H4-PR2) (3a: R = i-Pr, 3b: R = Ph) (Cp = η5-cyclopentadienyl) and Cp?2Ti(κ1-O-O-C6H4-PR2) (5a: R = i-Pr, 5b: R = Ph) (Cp? = η5-pentamethylcyclopentadienyl) were prepared by reactions of the 2-phosphinophenol ligand with different titanocene sources and fully characterised. Their catalytic activity depends on the steric influence of the cyclopentadienyl ligand, the coordination mode of the 2-phosphinoaryloxide ligand and on the used solvent. Complex 3a showed a turnover number of 43.2 in the neat substrate after 24 hours. EPR investigations were used to elucidate the fate of the Ti(iii) catalyst.
P-C-Activated Bimetallic Rhodium Xantphos Complexes: Formation and Catalytic Dehydrocoupling of Amine-Boranes
Johnson, Heather C.,Weller, Andrew S.
supporting information, p. 10173 - 10177 (2015/09/01)
{Rh(xantphos)}-based phosphido dimers form by P-C activation of xantphos (4,5-bis(diphenylphosphino)-9,9-dimethylxanthene) in the presence of amine-boranes. These dimers are active dehydrocoupling catalysts, forming polymeric [H2BNMeH]n from H3B·NMeH2 and dimeric [H2BNMe2]2 from H3B·NMe2H at low catalyst loadings (0.1 mol %). Mechanistic investigations support a dimeric active species, suggesting that bimetallic catalysis may be possible in amine-borane dehydropolymerization.
Synthesis and the thermal and catalytic dehydrogenation reactions of amine-thioboranes
Robertson, Alasdair P. M.,Haddow, Mairi F.,Manners, Ian
scheme or table, p. 8254 - 8264 (2012/09/22)
A series of trimethylamine-thioborane adducts, Me3N· BH2SR (R = tBu [2a], nBu [2b], iPr [2c], Ph [2d], C6F 5 [2e]) have been prepared and characterized. Attempts to access secondary and primary amine adducts of thioboranes via amine-exchange reactions involving these species proved unsuccessful, with the thiolate moiety shown to be vulnerable to displacement by free amine. However, treatment of the arylthioboranes, [BH2-SPh]3 (9) and C6F 5SBH2·SMe2 (10) with Me2NH and iPr2NH successfully yielded the adducts Me2NH· BH2SR (R = Ph [11a], C6F5 [12a]) and iPr 2NH·BH2SR (R = Ph [11b], C6F5 [12b]) in high yield. These adducts were also shown to be accessible via thermally induced hydrothiolation of the aminoboranes Me2N=BH 2, derived from the cyclic dimer [Me2N-BH 2]2 (13), and iPr2N=BH2 (14), respectively. Attempts to prepare the aliphatic thiolate substituted adducts R2NH·BH2SR′ (R = Me, iPr; R′ = tBu, nBu, iPr) via this method, however, proved unsuccessful, with the temperatures required to facilitate hydrothiolation also inducing thermal dehydrogenation of the amine-thioborane products to form aminothioboranes, R2N= BH(SR′). Thermal and catalytic dehydrogenation of the targeted amine-thioboranes, 11a/11b and 12a/12b were also investigated. Adducts 11b and 12b were cleanly dehydrogenated to yield iPr2N=BH(SPh) (22) and iPr2N=BH(SC6F5) (23), respectively, at 100 °C (18 h, toluene), with dehydrogenation also possible at 20 °C (42 h, toluene) with a 2 mol % loading of [Rh(μ-Cl)cod]2 in the case of the former species. Similar studies with adduct 11a evidenced a competitive elimination of H2 and HSPh upon thermolysis, and other complex reactivity under catalytic conditions, whereas the fluorinated analogue 12a was found to be resistant to dehydrogenation.
Catalytic dehydrogenation of dimethylamine borane by group 4 metallocene alkyne complexes and homoleptic amido compounds
Beweries, Torsten,Hansen, Sven,Kessler, Monty,Klahn, Marcus,Rosenthal, Uwe
, p. 7689 - 7692 (2011/09/20)
Dehydrogenation of Me2NH·BH3 (1) by group 4 metallocene alkyne complexes of the type Cp2M(L)(η2- Me3SiC2SiMe3) [Cp = η5- cyclopentadienyl; M = Ti, no L (2Ti); M = Zr, L = pyridine (2Zr)] and group 4 metal amido complexes of the type M(NMe2)4 [M = Ti (8Ti), Zr (8Zr)] is presented.
Heterogeneous dehydrocoupling of amine-borane adducts by skeletal nickel catalysts
Robertson, Alasdair P. M.,Suter, Riccardo,Chabanne, Laurent,Whittell, George R.,Manners, Ian
, p. 12680 - 12691 (2012/02/15)
Skeletal Ni, produced by the selective leaching of Al from a Ni/Al alloy, has been successfully employed in the catalytic dehydrogenation of various amineborane adducts. The combination of low cost and facile single-step synthesis make this system a potentially attractive alternative to the previously described precious metal and other first-row metal catalysts. The heterogeneous nature of the catalyst facilitates convenient product purification, and this is the first such system to be based on a first-row transition metal. Catalytic dehydrocoupling of Me2NH·BH3 (1) and Et2NH3 BH3 (5) was demonstrated using 5 mol % skeletal Ni catalyst at 20 °C and produced [Me2N·BH2]2 (2) and [Et2N-BH2]2/Et2NdBH2 (6), respectively. The related adduct iPr2NH3 BH 3 (7) was also dehydrogenated to afford iPr2NdBH2 (8) but with significant catalyst deactivation. Catalytic dehydrocoupling of MeNH2 3 BH3 (9) was found to yield the cyclic triborazane [MeNH-BH 2]3 (10) as the major product, whereas high molecular weight poly- (methylaminoborane) [MeNH-BH2]n (11) (Mw = 78 000 Da, PDI = 1.52) was formed when stoichiometric quantities of Ni were used. Similar reactivity was also observed with NH3 3 BH3 (12), which produced cyclic oligomers and insoluble polymers, [NH2-BH2] xx (14), under catalytic and stoichiometric Ni loadings, respectively. Catalyst recycling was hindered by gradual poisoning. A study of possible catalyst poisons suggested that BH3 was the most likely surface poison, in line with previous work on colloidal Rh catalysts. Catalytic borane adducts using skeletal Cu and Fe was also explored. Skeletal Cu was found to be a less active dehydrogenation catalyst for amine-borane adducts but also yielded poly(methylaminoborane) under stoichiometric conditions on reaction with MeNH2 · BH3 (9). Skeletal Fe was found to be completely inactive towardamine-borane dehydrogenationr
