Monoammoniate of Calcium Amidoborane: Synthesis, Structure, and Hydrogen-Storage Properties

Photoelectron spectroscopy and computational investigations of the electronic structures and noncovalent interactions of cyclodextrin-closo-dodecaborate anion complexes χ-CD·B12X122− (χ = α, β, γ; X = H, F)

We report a joint negative ion photoelectron spectroscopy and computational study on the electronic structures and noncovalent interactions of a series of cyclodextrin-closo-dodecaborate dianion complexes, χ-CD·B₁₂X₁₂²⁻ (χ = α, β, γ; X = H, F).

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

A magnesium complex (1) featuring a bidentate aminopyridinato ligand is a remarkably selective catalyst for the dehydrocoupling of amine-boranes. This reaction proceeds to completion with low catalyst loadings (1 mol %) under mild conditions (60 °C), exceeding previously reported s-block systems in terms of selectivity, rate, and turnover number (TON). Mechanistic studies by in situ NMR analysis reveals the reaction to be first order in both catalyst and substrate. A reaction mechanism is proposed to account for these findings, with the high TON of the catalyst attributed to the bidentate nature of the ligand, which allows for reversible deprotonation of the substrate and regeneration of 1 as a stable resting state.

Dehydrogenation of dimethylamine-borane mediated by Group 1 pincer complexes

Alkali metal carbazolido complexes are precatalysts for the dehydrogenation of Me₂NH·BH₃, where the cation plays a vital role in the reaction outcome.

In-Situ and Real-time Monitoring of Mechanochemical Preparation of Li2 Mg(NH2 BH3 )4 and Na2 Mg(NH2 BH3 )4 and Their Thermal Dehydrogenation

For the first time, in situ monitoring of uninterrupted mechanochemical synthesis of two bimetallic amidoboranes, M₂ Mg(NH₂ BH₃ )₄ (M=Li, Na), by means of Raman spectroscopy, has been applied. This approach allowed real-time observation of key intermediate phases, and a straightforward follow-up of the reaction course. Detailed analysis of time-dependent spectra revealed a two-step mechanism through MNH₂ BH₃ ⋅NH₃ BH₃ adducts as key intermediate phases which further reacted with MgH₂ , giving M₂ Mg(NH₂ BH₃ )₄ as final products. The intermediates partially take a competitive pathway toward the oligomeric M(BH₃ NH₂ BH₂ NH₂ BH₃ ) phases. The crystal structure of the novel bimetallic amidoborane Li₂ Mg(NH₂ BH₃ )₄ was solved from high-resolution powder diffraction data and showed an analogous metal coordination to Na₂ Mg(NH₂ BH₃ )₄ , but a significantly different crystal packing. Li₂ Mg(NH₂ BH₃ )₄ thermally dehydrogenates releasing highly pure H₂ in the amount of 7 wt.%, and at a lower temperature then its sodium analogue, making it significantly more viable for practical applications.

Lithium Hydrazinidoborane Ammoniate LiN₂H₃BH₃·0.25NH₃, a Derivative of Hydrazine Borane

Boron- and nitrogen-based materials have shown to be attractive for solid-state chemical hydrogen storage owing to gravimetric hydrogen densities higher than 10 wt% H. Herein, we report a new derivative of hydrazine borane N₂H₄BH₃, namely lithium hydrazinidoborane ammoniate LiN₂H₃BH₃·0.25NH₃. It is easily obtained in ambient conditions by ball-milling N₂H₄BH₃ and lithium amide LiNH₂ taken in equimolar amounts. Both compounds react without loss of any H atoms. The molecular and crystallographic structures of our new compound have been confirmed by NMR/FTIR spectroscopy and powder X-ray diffraction. The complexation of the entity LiN₂H₃BH₃ by some NH₃ has been also established by thermogravimetric and calorimetric analyses. In our conditions, LiN₂H₃BH₃·0.25NH₃ has been shown to be able to release H₂ at temperatures lower than the parent N₂H₄BH₃ or the counterpart LiN₂H₃BH₃. It also liberates non-negligible amounts of NH₃ at temperatures lower than 100 °C. This is actually quite detrimental for chemical H storage, but alternatively LiN₂H₃BH₃·0.25NH₃ might be seen as a potential NH₃ carrier.

First-principles study of decomposition mechanisms of Mg(BH4)2·2NH3 and LiMg(BH4)3·2NH3

Compared to that of Mg(BH₄)₂·2NH₃, LiMg(BH₄)₃·2NH₃ has a relatively high NH₃ diffusion barrier and H₂ formation barrier.

The significance of secondary interactions during alkaline earth-promoted dehydrogenation of dialkylamine-boranes

Reactions of anilidoimine magnesium n-butyl and calcium bis(trimethylsilyl)amide derivatives with Me₂NH·BH₃ at 25 °C resulted in the isolation of complexes containing [NMe₂BH₂NMe₂BH₃]⁻ and [NMe₂BH₃]⁻ anions respectively.

Synthesis, structure and the dehydrogenation mechanism of calcium amidoborane hydrazinates

The calcium amidoborane hydrazinates, Ca(NH₂BH₃)₂·nN₂H₄, were firstly synthesized and exhibited superior dehydrogenation properties compared with those of pristine Ca(NH₂BH₃)₂.

Alkali metal-mediated dehydrocoupling of Me2NH·BH3

Bis(trimethylsilyl)amide derivatives of the group 1 elements (Li, Na, K) are competent pre-catalysts for the dehydrocoupling of Me2NH·BH3 via the formation of intermediates containing [H3BNMe2BH2Me2N](-) anions.

Preparation and dehydrogenation properties of lithium hydrazidobis(borane) (LiNH(BH3)NH2BH3)

LiNH(BH3)NH2BH3, the first example of metal-substituted hydrazine bisborane (HBB), is synthesized via the reaction between HBB and n-butyllithium in ether solution. (11)B NMR and Fourier transform infrared spectroscopy indicate a new structure, in which one of the N-H bonds is replaced by a N-Li bond. The X-ray diffraction pattern of the product also indicates the formation of a new crystal structure. This compound releases hydrogen at 126 and 170 °C with satisfactory purity and exhibits superior hydrogen storage properties compared with HBB. Differential scanning calorimetry measurement suggests the dehydrogenation reaction of this compound is less exothermic than that of HBB.

Structural prediction, analysis and decomposition mechanism of solid M(NH2BH3)n (M = Mg, Ca and Al)

Crystal structures of multivalent metal amidoboranes (CaAB, MgAB, AlAB) with their thermodynamic properties and dehydrogenation mechanisms have been obtained theoretically.