6569-51-3Relevant articles and documents
Osmium-promoted dehydrogenation of amine-boranes and B-H bond activation of the resulting amino-boranes
Esteruelas, Miguel A.,Fernandez, Israel,Lopez, Ana M.,Mora, Malka,Onate, Enrique
, p. 1104 - 1107 (2014)
The five-coordinate osmium complex OsH(SH)(CO)(PiPr 3)2, containing an electrophilic center bonded to the soft hydrogen sulfide ligand, promotes dehydrogenation of amine-boranes and captures the amino-borane products, form
Borazine Thermal Decomposition in Unsaturated Vapor
Zavgorodnii,Timoshkin, A. Yu.
, p. 2476 - 2479 (2018)
The temperature dependence of vapor pressure over liquid and solid borazine has been measured by static tensiometry method with a membrane null-manometer at 200–259 K. Gas-phase heat-induced decomposition of borazine in its unsaturated vapor has been studied over the 373–473 K range.
Low-temperature synthesis of highly crystallized hexagonal boron nitride sheets with Li3N as additive agent
Yuan, Sheng,Toury, Bérangère,Benayoun, Stéphane,Chiriac, Rodica,Gombault, Fran?ois,Journet, Catherine,Brioude, Arnaud
, p. 5507 - 5513 (2014)
Highly crystallized hexagonal boron nitride (h-BN) sheets were obtained by a versatile method modifying the original synthesis by using an additive agent and, as a consequence, decreasing the temperature for the ceramization step (1200-1400 °C). This synthesis is based on the polymer-derived ceramics (PDCs) route using liquid-state polyborazylene (PBN) mixed with lithium nitride (Li3N) micropowders as additive agent. We have demonstrated that incorporation of Li3N as a crystallization promoter allows the onset of crystallization of h-BN at lower temperatures. Consequently, a high crystallization rate can be obtained from 1000 °C for bulk boron nitride, whereas the temperature has to be 1600-1800 °C under classical conditions. A series of samples incorporating Li3N (5 wt.-%) and annealed at various temperatures from 600 to 1400 °C was prepared and structurally characterized by Raman spectroscopy, XRD analyis, and TEM. Well-crystallized sheets with thicknesses of nanometers can be easily obtained by applying this method.
Preparation of h-BN nano-tubes, -bamboos, and -fibers from borazine oligomer with alumina porous template
Wang, Yuting,Shimada, Shiro,Yamamoto, Yasunori,Miyaura, Norio
, p. 251 - 256 (2008)
h-BN nano-tubes, -bamboos, and -fibers were prepared separately from borazine oligomers using an alumina porous template at different wetting times of 20 h, 40 h and 2 weeks at room temperature, respectively. The borazine oligomer in the template was transformed to the h-BN nano-materials by two-step heat-treatment at 600 and 1200 °C in flowing N2. The FT-IR result confirmed the formation of BN. TEM and SEM images showed the formation of the nano-tubes in diameters 200-300 nm with thin walls about 10-20 nm thick, nano-bamboos 200-300 nm wide with knots at the separations of 0.5-1 μm, and the nano-fibers 15-20 μm long with fine crystallized BN particles. The mechanism for the formation of h-BN nano-tubes, -bamboos and -fibers is proposed.
Efficient catalytic conversion of ammonia borane to borazine and its use for hexagonal boron nitride (white graphene)
Kim, Sung-Kwan,Cho, Hyunjin,Kim, Myung Jong,Lee, Hee-Jun,Park, Jin-Hyung,Lee, Young-Boo,Kim, Hwan Chul,Yoon, Chang Won,Nam, Suk Woo,Kang, Sang Ook
, p. 1976 - 1981 (2013)
Nickel nanoparticles (NiNPs) prepared in tetraglyme (TG) efficiently catalyzed the conversion of ammonia borane (AB, NH3BH3) to borazine (B3N3H6). Under the optimized conditions, 3 mol% of the NiNPs were introduced into a 1.5 M AB solution in TG and held at 80 °C for 6 h under a dynamic vacuum that was maintained at 30 torr. Borazine was isolated through a series of -45 °C, -78 °C, and -196 °C traps to give (-78 °C trap) pure borazine in 53% yield. The borazine produced was then utilized as a molecular precursor for high quality h-BN (white graphene) and large area h-BN sheets were prepared by applying low pressure chemical vapor deposition (LPCVD). Ultra-thin (single to few layers) h-BN was synthesized on Ni foil at the optimal ratio between borazine and NH3, and the number of layers was tuned by varying the NH3 partial pressure. The Royal Society of Chemistry 2013.
Dehydrocoupling of amine boranes via tin(IV) and tin(II) catalysts
Erickson, Karla A.,Wright, Dominic S.,Waterman, Rory
, p. 541 - 545 (2014)
Catalytic dehydrocoupling of primary and secondary amine boranes and ammonia borane using tin(IV) and tin(II) catalysts is presented. These tin compounds have been demonstrated to dehydrocouple phosphines where catalytic activity was dependent on metal oxidation state. In contrast, the mechanism of amine borane dehydrocoupling appears to be substrate dependent. The most sterically encumbered substrate, tBuNH2BH3, appears to engage in β-hydrogen elimination based on the observation of tBuN = BH2, whereas Me2NHBH3 appears to be involved in a chain-growth process as evidenced by linear diborazane and the absence of amino borane. Though these tin catalysts are moderately active in the spectrum of amine borane dehydrocoupling catalysts, the dependence of mechanism on substrate appears to be unique.
Thermolysis and solid state NMR studies of NaB3H8, NH3B3H7, and NH4B3H 8
Huang, Zhenguo,Eagles, Mitch,Porter, Spencer,Sorte, Eric G.,Billet, Beau,Corey, Robert L.,Conradi, Mark S.,Zhao, Ji-Cheng
, p. 701 - 708 (2013)
In an effort to broaden the search for high-capacity hydrogen storage materials, three triborane compounds, NaB3H8, NH 3B3H7, and NH4B3H 8, were studied. In addition to hydrogen, thermal decomposition also releases volatile boranes, and the relative amounts and species depend on the cations (Na+, NH4+) and the Lewis base (NH 3). Static-sample hydrogen NMR is used to probe molecular motion in the three solids. In each case, the line width decreases from low temperatures to room temperature in accordance with a model of isotropic or nearly isotropic reorientations. Such motions also explain a deep minimum in the relaxation time T1. Translational diffusion never appears to be rapid on the 10 -5 s time scale of NMR.
Thermal decomposition of cyclotriborazane
Schellenberg,Kriehme,Wolf
, p. 103 - 108 (2007)
Cyclotriborazane (CTB), B3N3H12, is a crystalline white solid, which decomposes above 400 K to hydrogen and a few other products, depending on the reaction conditions. In this work we present investigations of the thermal decomposition of both the neat compound and CTB dissolved in diglyme and tetraglyme. Several thermophysical and analytical methods, such as differential scanning calorimetry (DSC), thermogravimetry (TG), mass spectroscopy (QMS), and 11B nuclear magnetic resonance spectroscopy (NMR) have been used for this investigation. The decomposition of the neat substance releases 3.1 mol H2/mol CTB and leads to a polymeric products and borazine. In open vessels, sublimation as a competing process also occurs. The enthalpy of the decomposition process (ΔRHs) has been determined as ΔRHs = -34.0 ± 2.9 kJ/mol. In contrast to the thermal decomposition of the pure substance, the decomposition in polyethers, such as diglyme and tetraglyme, leads above 370 K to borazine and small amounts of soluble oligomeric borazine species. Also BH3 group containing species are occurring as intermediates. In these systems no precipitation was detected. DSC measurements show for the decomposition in solution several strong exothermic effects. The overall decomposition enthalpy in diglyme is given by ΔRHd = -32.0 ± 2.8 kJ/mol and in tetraglyme by ΔRHt = -48.0 ± 4.7 kJ/mol. The enthalpy of solution of cyclotriborazane was determined in diglyme and in tetraglyme with the values ΔDHd = -2.1 ± 0.2 kJ/mol and ΔDHt = -4.6 ± 0.5 kJ/mol, respectively.
Dehydrogenation of ammonia-borane by Shvo's catalyst
Conley, Brian L.,Williams, Travis J.
, p. 4815 - 4817 (2010)
Shvo's cyclopentadienone-ligated ruthenium complex is an efficient catalyst for the liberation of exactly two molar equivalents of hydrogen from ammonia-borane, a prospective hydrogen storage medium. The mechanism for the dehydrogenation features a ruthenium hydride resting state from which dihydrogen loss is the rate-determining step.
The mechanism of borane-amine dehydrocoupling with bifunctional ruthenium catalysts
Marziale, Alexander N.,Friedrich, Anja,Klopsch, Isabel,Drees, Markus,Celinski, Vinicius R.,Schmedt Auf Der Guenne, Joern,Schneider, Sven
, p. 13342 - 13355 (2013)
Borane-amine adducts have received considerable attention, both as vectors for chemical hydrogen storage and as precursors for the synthesis of inorganic materials. Transition metal-catalyzed ammonia-borane (H3N-BH 3, AB) dehydrocoupling offers, in principle, the possibility of large gravimetric hydrogen release at high rates and the formation of B-N polymers with well-defined microstructure. Several different homogeneous catalysts were reported in the literature. The current mechanistic picture implies that the release of aminoborane (e.g., Ni carbenes and Shvo's catalyst) results in formation of borazine and 2 equiv of H2, while 1 equiv of H 2 and polyaminoborane are obtained with catalysts that also couple the dehydroproducts (e.g., Ir and Rh diphosphine and pincer catalysts). However, in comparison with the rapidly growing number of catalysts, the amount of experimental studies that deal with mechanistic details is still limited. Here, we present a comprehensive experimental and theoretical study about the mechanism of AB dehydrocoupling to polyaminoborane with ruthenium amine/amido catalysts, which exhibit particularly high activity. On the basis of kinetics, trapping experiments, polymer characterization by 11B MQMAS solid-state NMR, spectroscopic experiments with model substrates, and density functional theory (DFT) calculations, we propose for the amine catalyst [Ru(H)2PMe3{HN(CH2CH2PtBu 2)2}] two mechanistically connected catalytic cycles that account for both metal-mediated substrate dehydrogenation to aminoborane and catalyzed polymer enchainment by formal aminoborane insertion into a H-NH 2BH3 bond. Kinetic results and polymer characterization also indicate that amido catalyst [Ru(H)PMe3{N(CH2CH 2PtBu2)2}] does not undergo the same mechanism as was previously proposed in a theoretical study.
