Benjamin L. Davis

Potassium(I) amidotrihydroborate: structure and hydrogen release.

Potassium(I) amidotrihydroborate (KNH(2)BH(3)) is a newly developed potential hydrogen storage material representing a completely different structural motif within the alkali metal amidotrihydroborate group. Evolution of 6.5 wt % hydrogen starting at temperatures as low as 80 degrees C is observed and shows a significant change in the hydrogen release profile, as compared to the corresponding lithium and sodium compounds. Here we describe the synthesis, structure, and hydrogen release characteristics of KNH(2)BH(3).

Physical, structural, and dehydrogenation properties of ammonia borane in ionic liquids

Ionic liquids (ILs) are excellent solvents for the dehydrogenation of ammonia borane (AB); however, the basic properties that allow efficient dehydrogenation are still unclear. In this report, density, viscosity, melting/freezing/glass transition temperature, solubility, and the dehydrogenation properties, including impurity gas quantification, of AB-imidazolium-based IL solutions were studied. Note that ILs can solubilize 32–35 wt% of AB, and the liquid AB–IL solutions have densities of ∼0.9 g cm−3, viscosities similar to motor oil (100–250 cP), and glass transition temperatures below −50 °C. AB–ILs are stable at room temperature for several weeks with minimal hydrogen generation, although some hydrolysis occurs immediately upon mixing as a result of trace water content. Between 80 and 130 °C, more than 2 mol H2/AB are desorbed from AB–ILs with limited impurity emissions. Furthermore, there is no reaction between AB and ILs upon dehydrogenation, and structural analysis reveals a complex solid solution.

Enabling ammonia-borane: co-oligomerizaiton of ammonia-borane and amine-boranes yield liquid products

In contrast to neat ammonia-borane (AB), the thermal decomposition of AB with N-substituted amine-boranes yields a liquid product after extended heating and H2 release. NMR and GPC data indicate that co-oligomerization has occurred. These results show promise for developing high energy density AB-based fuel formulations for automotive applications.

N-substituted amine-borane ionic liquids as fluid phase, hydrogen storage materials

A selection of task specific N-substituted amine-borane ionic liquids (N-ABILs) were synthesized in good yield using silyl protecting groups with the aim of developing hydrogen (H2) storing fuels for automotive applications. A new anhydrous anion exchange method, based on trimethylsilyl reagents, was employed so sensitive pendant functionalities like borane could be incorporated. Controlled thermoylsis of N-ABILs indicate members of this class may be liquids pre- and post-dehydrogenation, joining a relatively small population of putative H2 storing fuels that can be readily loaded/unloaded from a vehicle. N-ABILs were also blended with ammonia-borane to improve overall H2 capacity, in one case by ∼2.5×. The products of thermolysis consist of co-oligomerized BN species and highly pure (<1% impurity) H2 gas.

Early-lanthanide(III) acetonitrile–solvento adducts with iodide and noncoordinating anions

Dissolution of LnI3 (Ln = La, Ce) in acetonitrile (MeCN) results in the highly soluble solvates LnI3(MeCN)5 [Ln = La (1), Ce (2)] in good yield. The ionic complex [La(MeCN)9][LaI6] (4), containing a rare homoleptic La(3+) cation and anion, was also isolated as a minor product. Extending this chemistry to NdI3 results in the consistent formation of the complex ionic structure [Nd(MeCN)9]2[NdI5(MeCN)][NdI6][I] (3), which contains an unprecedented pentaiodide lanthanoid anion. Also described is the synthesis, isolation, and structural characterization of several homoleptic early-lanthanide MeCN solvates with noncoordinating anions, namely, [Ln(MeCN)9][AlCl4]3 [Ln = La (5), Ce (6), Nd (7)]. Notably, complex 6 is the first homoleptic cerium MeCN solvate reported to date. All reported complexes were structurally characterized by X-ray crystallography, as well as by IR spectroscopy and CHN elemental analysis. Complexes 1-3 were also characterized by thermogravimetric analysis coupled with mass spectrometry to further elucidate their bulk composition in the solid-state.

Formation of benzodiazaborolanes from borazine

Phenylenediamines are shown to form benzodiazaborolanes upon reaction with borazine, essentially extracting the B-H bonds. This surrogate for partially dehydrogenated ammonia borane provides useful insight into potential regeneration strategies for ammonia borane spent fuel.