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The catalytic effect of rare-earth hydrogen storage alloy is investigated for dehydrogenation of alane, which shows a significantly reduced onset dehydrogenation temperature (86 °C) with a high-purity hydrogen storage capacity of 8.6 wt% and an improved dehydrogenation kinetics property (6.3 wt% of dehydrogenation at 100 °C within 60 min). The related mechanism is that the catalytic sites on the surface of the hydrogen storage alloy and the hydrogen storage sites of the entire bulk phase of the hydrogen storage reduce the dehydrogenation temperature of AlH3 and improve the dehydrogenation kinetic performance of AlH3. This facile and effective method significantly improves the dehydrogenation of AlH3 and provides a promising strategy for metal hydride modification.

The decomposition of aluminum hydride complexes with trimethylamine and N-heterocyclic carbene—1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene was studied by a static tensimetric method with a membrane null-manometer. The AlH3·NMe3 complex passes into vapor in the form of monomeric molecules and in unsaturated vapor slowly decomposes at 70‒80°С into solid aluminum, gaseous trimethylamine, and hydrogen. The decomposition is accompanied by an induction period, the duration of which decreases as temperature increases. The AlH3 complex with carbene slowly decomposes at 170‒200°С with a rate practically independent of temperature.

Amidoenoate (AME = {ethyl-3-(R-amido)but-2-enoate}) complexes of aluminium and gallium, of the type: [AlCl2(AMER)] R = iPr (1-Al); [AlCl(AMER)2] R = iPr (2-Al), Dip (3-Al); [GaCl2(AMER)] R = iPr (1-Ga) and [GaCl(AMER)2] R = iPr (2-Ga), Dip (3-Ga), have been synthesised (iPr = isopropyl, Dip = 2,6-diisopropylphenyl). The coordination chemistry of these complexes has been studied in relation to precursor suitability. Investigations into the reactivity of the aluminium and gallium amidoenoate complexes involved reactions with hydride sources including alkali metal hydride salts, alkylsilanes, and magnesium hydride species and magnesium(I) dimers. The isolation of alkyl metal amidoenoate precursors including an aluminium hydride amidoenoate, [AlH(AMEDip)2] (4-Al) and dimethyl gallium amidoenoates [GaMe2(AMEDip)] (4-Ga), [GaMe2(AMEiPr)] (5-Ga) concluded the synthetic studies. A selection of the isolated complexes were used as precursors by aerosol assisted chemical vapour deposition (AACVD) at 500 °C. Thin films of either amorphous Al2O3 or Ga2O3 were deposited and subsequently annealed at 1000 °C to improve the materials’ crystallinity. The films were characterised by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-visible (UV-vis) spectroscopy and energy dispersive X-ray analysis (EDXA)

α- and γ-alumina (α-Al2O3 and γ-Al2O3) are used to model the surface oxide layer of AlH3 to investigate the micro-mechanism for the interactions of three energetic plasticizers: Bis-2,2-dinitropropyl formal (BDNPF), N-butyl-N-(2-nitroxyethyl) nitramine (BuNENA) and nitroglycerin (NG) with AlH3 surface oxidation layers. First principle density functional theory (DFT) calculations with all-electron double numerical basis functions (DND) are employed. It is found that three energetic plasticizers can be strongly adsorbed by the oxide film of AlH3 and release a large amount of heat. Moreover, BuNENA and NG containing -ONO2 groups easily undergo barrierless decomposition reactions on the α-Al2O3 (0001) surface and spontaneously produces NO2 radicals, causing significant changes in the structures of BuNENA and NG molecules as well as of the α-Al2O3 (0001) surface. Furthermore, NG can also undergo a barrierless decomposition reaction on the γ-Al2O3 (110) surface. However, BuNENA does not decompose on the γ-Al2O3 (110) surface, and it is not easy for BDNPF to decompose on either α-Al2O3 (0001) or γ-Al2O3 (110) surfaces; hence, it remains relatively stable. According to these results, it is suggested that the order of compatibility among the three energetic plasticizers with AlH3 is BDNPF > BuNENA > NG.

AlH 3 (alane) is considered as an ideal one-off compact hydrogen storage material thanks to its high storage capacity and moderate decomposition temperature. However, application has been hindered by the lack of direct hydrogen reversibility, i.e. regeneration of AlH 3 directly from the reaction of spent Al with hydrogen under mild conditions. Herein, we investigated the effect of nanoconfinement on the properties of AlH 3 and the potential of this approach toward the direct release and uptake of hydrogen by nanosized Al. AlH 3 was confined within the mesopores of a high surface area graphite (HSAG). The decomposition of the nanoconfined AlH 3 was detected 50 °C lower than the bulk, showing some effect of nanoconfinement on the overall temperature for hydrogen release. Some hydrogen uptake was also observed at 150 °C and 60 bar hydrogen pressure, and this indicates that reversible release of hydrogen with alane under moderate conditions of pressure and temperature may be possible.

The most important factor behind the intriguing differences between the geometries of the M'AlH3 (M' = Mg, Ca) molecules is shown to be dynamical electron correlation and not intramolecular Coulombic interactions, as previously thought. Spin-coupled generalized valence bond (SCGVB) calculations reveal the different bonding situations in the two molecules at their optimal geometries but do not explain why these geometries differ so much; the solution to this conundrum comes instead from detailed analysis of coupled-cluster (CCSD(T)) energies at model and optimal geometries.

Historically used in stoichiometric hydroalumination chemistry, recent advances have transformed aluminium hydrides into versatile catalysts for the hydroboration of unsaturated multiple bonds. This catalytic ability is founded on the defining reactivity of aluminium hydrides with alkynes and alkenes: 1,2‐hydroalumination of the unsaturated π‐system. This manuscript reports the aluminium hydride catalyzed dehydroborylation of terminal alkynes. A tethered intramolecular amine ligand controls reactivity at the aluminium hydride centre, switching off hydroalumination and instead enabling selective reactions at the alkyne C−H σ‐bond. Chemoselective C−H borylation was observed across a series of aryl‐ and alkyl‐substituted alkynes (21 examples). On the basis of kinetic and density functional theory studies, a mechanism in which C−H borylation proceeds by σ‐bond metathesis between pinacolborane (HBpin) and alkynyl aluminium intermediates is proposed., The aluminium hydride catalyzed dehydroborylation of terminal alkynes is reported. By using a tethered‐intramolecular‐amine Lewis base as a ligand at the aluminium hydride centre the reactivity is controlled. Hydroalumination is switched off and selective reactions at the alkyne C−H σ‐bond are enabled.

Hybrid propulsion offers safe, reliable and environment friendly alternative to conventional systems. There is a wide range of propellants and additives reported for hybrid propulsion. In this paper some energetic particles comprising metals, and light metal hydrides and their advantages in terms of regression behavior are discussed. Additive particles like aluminium, boron, boron carbide, tungsten, iron, carbon, magnesium, magnesium hydride, aluminium hydride, lithium aluminium hydride, ammonium perchlorate and ammonia borane are discussed. Regression rate enhancement of 20%-150% has been reported and found to be dependent on additive percentage. Metals have high density and heat of oxidation which helps in regression rate augmentation. Metal hydrides are good source of hydrogen varying from 7.6% for Magnesium hydride to 19.6% for Ammonia borane. These hydrides release nascent hydrogen during combustion and improve regression rate thereby boosting specific impulse and characteristic velocity of the rocket. Energetic particle laden hybrid rocket fuel has potential to make chemical propulsion safer, economical and sustainable.

Aluminium hydride (AlH3) is a promising hydrogen storage material due to its competitive hydrogen storage density and moderate decomposition temperature. However, there is no convenient way to prepare/regenerate AlH3 from (spent) Al by direct hydrogenation. Herein, we report on a novel approach to generate AlH3 from the decomposition of triethylaluminium (Et3Al) under mild hydrogen pressures (10 MPa) with the use of surfactants. With tetraoctylammonium bromide (TOAB), the synthesis led to the formation of nanosized AlH3 with the known α phase, and these nanoparticles released hydrogen from 40 °C instead of the 125 °C observed with bulk α-AlH3. However, when tetrabutylammonium bromide (TBAB) was used instead of TOAB, larger nanoparticles believed to be related to the formation of β-AlH3 were obtained, and these decomposed through a single exothermic process. Despite the possibility to form α-AlH3 under low conditions of temperature (180 °C) and pressure (10 MPa), TOAB stabilised AlH3 was found to be irreversible when subjected to hydrogen cycling at 150 °C and 7 MPa hydrogen pressure.

Aluminium hydride (AlH3) is a promising hydrogen storage material because it possesses a high theoretical hydrogen capacity of 10.01 wt%. However, the stability and decomposition mechanism of some AlH3 polymorphs (e.g., γ-AlH3) still remain unclear. In this work, the hydrogen desorption behaviours of γ-AlH3 with or without TiF3 addition were investigated by hydrogen desorption measurement and thermal analysis. It was revealed that the decompositions of the outer layer and the inner part of γ-AlH3 particle follow diverse decomposition mechanisms. The outer layer of γ-AlH3 particle tends to decompose directly, while the inner part of γ-AlH3 particle prefers to first transform to more stable α-AlH3 and then decompose. TiF3 addition significantly lowers the temperature for the direct decomposition of outer layer γ-AlH3 by about 30 °C but scarcely impacts the decomposition of inner part γ-AlH3, which further confirms the decomposition mechanism of γ-AlH3. It was suggested that the particle size plays an important role in the thermal stability of γ-AlH3. The results of this work will help understanding the decomposition mechanisms of other AlH3 polymorphs for hydrogen storage.

Lithium borohydride (LiBH4) possesses a very high hydrogen capacity (18.5 wt%) but suffers from high thermal stability. In this work, the as-prepared aluminium hydride (AlH3) was ball milled with LiBH4 forming 2LiBH4 + AlH3 composite to improve the hydrogen desorption properties of LiBH4. Hydrogen desorption measurements showed that a hydrogen capacity of 11.2 wt% is obtained from the 2LiBH4 + AlH3 composite and the desorption temperature of LiBH4 with AlH3 addition is reduced by more than 30 °C. AlH3 is better as an Al source than the as-received Al in that the hydrogen desorption extent of AlH3-doped LiBH4 reaches 70%, while it is 54% and 61% for the pure LiBH4 and the Al-doped LiBH4. This is due to the brittle and oxide-free nature of AlH3. Microstructure investigations showed that during heating process, the 2LiBH4 + AlH3 composite undergoes AlH3 decomposition forming Al* and releasing hydrogen, followed by the decomposition of LiBH4. LiBH4 will react with Al* forming AlB2 and Li Al B compounds during its decomposition, which contributes to the improved hydrogen desorption properties of LiBH4.

We report an efficient protocol for the catalytic chemo-selective reduction of tert-amides with pinacolborane (HBpin) to afford the corresponding amines in high yields using aluminium complexes [κ2-{Ph2P(X)NC9H6N}Al(Me)2] [X = S (2a), Se (2b)] as pre-catalysts at room temperature. The aluminium complexes were prepared from the reaction of [Ph2P(X)NC9H6N] [X = S (1a), Se (1b)] and trimethylaluminium in toluene. The solid-state structure of complex 2b is established. Tertiary amides with a wide array of electron-withdrawing and electron-donating functional groups were easily converted to the desired products through the selective cleavage of the amides' C[double bond, length as m-dash]O bond by aluminium hydride as an active species. A kinetic study of the catalytic reaction is also reported.

A series of novel β-diketiminate stabilised aluminium borohydrides of the type (Nacnac)Al(R){H2(9-BBN)} has been synthesised offering variation in both the auxiliary R substituent and in the Nacnac backbone itself. A number of these complexes show unusual dissociation of the borane from the aluminium hydride in solution under ambient conditions. The lability of the borane is shown (by variable temperature NMR analyses) to be influenced by the electronic character of both the aluminium-bound R substituent and the Nacnac ligand itself, such that electron-withdrawing substituents lead to greater dissociation of the borane. Comparison of these complexes with related systems featuring the tetrahydroborate [BH4]− ligand illustrates the impact of the boron-bound substituents on the ability of the borane fragment to dissociate from the aluminium hydride. This dissociative behaviour is shown to be highly influential on the ability of the borohydride complexes to reduce carbon dioxide in a stoichiometric manner.

Ternary hydride of LiBH 4 –MgH 2 –NaAlH 4 confined into carbo n aerogel scaffold (CAS) via melt infiltration for reversible hydrogen storage is proposed. Nanoconfinement of hydrides into CAS is obtained together with surface occupation of some phases, such as Al and/or LiH. Regarding nanoconfinement, not only multiple-step decomposition of LiBH 4 –MgH 2 –NaAlH 4 hydride reduces to about single step, but also reduction of dehydrogenation temperature is significantly observed, for example, ∆ T up to 70 °C regarding last dehydrogenation step. Moreover, decomposition of NaBH 4 in nanoconfined sample can be done at 360 °C (dehydrogenation temperature in this study), which is 115 and 180 °C lower than that of NaBH 4 in milled LiBH 4 –MgH 2 –NaAlH 4 and bulk NaBH 4 , respectively. The reaction of LiBH 4 +NaAlH 4 →LiAlH 4 +NaBH 4 takes place during nanoconfinement and the decomposition of LiAlH 4 is observed, resulting deficient hydrogen content liberated. However, hydrogen content released (1st cycle) and reproduced (2nd–4th cycles) from this ternary hydride enhances up to 11% and 22% of full hydrogen storage capacity due to nanoconfinement. After rehydrogenation ( T =360 °C and P (H 2 )=50 bar H 2 for 12 h), NaBH 4 , MgH 2 , and Li 3 AlH 6 are reversible, whereas Li 3 AlH 6 and NaBH 4 in milled sample cannot be recovered due to deficient hydrogen pressure ( T =360 °C and P (H 2 )=80 bar) and probably evaporation of molten sodium during dehydrogenation, respectively. The latter results in inferior hydrogen content reproduced from milled sample to nanoconfined sample.

Boron hydride clusters are an extremely diverse compound class, which are of enormous importance to many areas of chemistry. Despite this, stable aluminium hydride analogues of these species have remained staunchly elusive to synthetic chemists. Here, we report that reductions of an amidinato-aluminium(III) hydride complex with magnesium(I) dimers lead to unprecedented examples of stable aluminium(I) hydride complexes, [(ArNacnac)Mg]2[Al6H6(Fiso)2] (ArNacnac = [HC(MeCNAr)2]−, Ar = C6H2Me3-2,4,6 Mes; C6H3Et2-2,6 Dep or C6H3Me2-2,6 Xyl; Fiso = [HC(NDip)2]−, Dip = C6H3Pri2-2,6), which crystallographic and computational studies show to possess near neutral, octahedral hypercloso-hexaalane, Al6H6, cluster cores. The electronically delocalised skeletal bonding in these species is compared to that in the classical borane, [B6H6]2−. Thus, the chemistry of classical polyhedral boranes is extended to stable aluminium hydride clusters for the first time., While polyhedral boron hydride complexes have found application in a number of diverse fields, the isolation of stable aluminium analogues remains highly challenging. Here, Jones and colleagues demonstrate that reduction of an amidinato-aluminum(III) hydride complex with magnesium(I) dimers affords stable aluminium(I) hydride compounds.

Hydrodefluorination reactions (HDF) of per- and polyfluorinated olefins and arenes by cheap aluminum alkyl hydrides in non-coordinating solvents can be catalyzed by O and N donors. TONs with respect to the organocatalysts of up to 87 have been observed. Depending on substrate and concentration, high selectivities can be achieved. For the prototypical hexafluoropropene, however, low selectivities are observed (E/Z≈2). DFT studies show that the preferred HDF mechanism for this substrate in the presence of donor solvents proceeds from the dimer Me4 Al2 (μ-H)2 ⋅THF by nucleophilic vinylic substitution (SN V)-like transition states with low selectivity and without formation of an intermediate, not via hydrometallation or σ-bond metathesis. In the absence of donor solvents, hydrometallation is preferred but this is associated with inaccessibly high activation barriers at low temperatures. Donor solvents activate the aluminum hydride bond, lower the barrier for HDF significantly, and switch the product preference from Z to E. The exact nature of the donor has only a minimal influence on the selectivity at low concentrations, as the donor is located far away from the active center in the transition states. The mechanism changes at higher donor concentrations and proceeds from Me2 AlH⋅THF via SN V and formation of a stable intermediate, from which elimination is unselective, which results in a loss of selectivity.

New molecular aluminium chloride amides [Cl2AlNEt2]2 and [HClAlNEt2]2 were prepared by salt-elimination reactions from lithium diethylamide and aluminium hydride dichloride diethyl-etherate or aluminium chloride, respectively. With LiBH4 in n-hexane they form the new boranates [(BH4)2AlNEt2]2 and [H(BH4)AlNEt2]2. X-ray single crystal structure analyses reveal dimeric molecules with non-planar four-membered Al2N2 rings in the solid state ([Cl2AlNEt2]2 (1): Pnma, V = 1606.3(2) A3, Z = 4; [HClAlNEt2]2 (2): Pnma, V = 1453.7(2) A3, Z = 4; [(BH4)2AlNEt2]2 (3): C2/c, V = 1810.8(2) A3, Z = 4; [H(BH4)AlNEt2]2 (4): Pnma, V = 1540.8(3) A3, Z = 4). Bond lengths and angles are in the usual range for such compounds and torsion angles within the Al2N2 rings vary from 1° to 14°. The packings of the dimeric molecules in compounds 1, 2, and 4 resemble a distorted hexagonal closest packing. NMR spectra corroborate the molecular structures from the solid state. CVD experiments with [HClAlNEt2]2 (2) as a single-source precursor yield thin aluminium layers. [H(BH4)AlNEt2]2 (4) is the first structurally characterized hydride tetrahydridoborate compound of aluminium.

Polyhydroxylated piperidines are a functionally rich class of biologically active molecules that have broad therapeutic potential. Recently developed aza-[4 + 3] cycloadditions of putative aza-oxyallylic cations provide heterocyclic scaffolds that enabled a concise synthesis of polyhydoxylated piperidines. Chemoselective amide reduction and reductive hemiaminal ring opening was achieved in one pot by the action of aluminium hydride generated in situ via aluminium chloride and lithium aluminium hydride. Aziridinium ion mediated ring contraction and chloride displacement was triggered by silver acetate, followed by simple acetate hydrolysis using potassium carbonate to give four tetrahydropyridine diols. Olefin oxidation by osmium tetroxide installed the final hydroxyl groups, which yielded four novel polyhydroxylated N-alkoxypiperidines in good overall yield and high diastereoselectivity.

Substituted bis(iminophosphoranyl)methanes are CH acidic compounds that can form complexes with formally dianionic central carbon centres. The reaction of H2C(Ph2P=NDip)2 (≡ H2L), Dip = 2,6-diisopropylphenyl, with one equivalent of di-n-butylmagnesium afforded the methanide complex [HLMgnBu] 1. Treatment of complex 1 with phenylsilane in aromatic solvents at elevated temperatures afforded the methanediide complex [(LMg)2] 2 presumably via the MgH intermediate [(HLMgH)n] (n = 1 or 2). The reaction of 1 with LiAlH4 in diethyl ether yielded the AlH complex [HLAlH2] 3. Alternatively, this complex was also obtained from the reaction of H2L with AlH3∙NMe3. The molecular structures of [HLMgnBu] 1, [(LMg)2] 2, and [HLAlH2] 3 are reported. Complex 3 shows no sign of H2 elimination to a methanediide species at elevated temperatures in contrast to the facile elimination of the putative reaction intermediate [(HLMgH)n] (n = 1 or 2) to form [(LMg)2] 2. The chemical properties of complex 2 were investigated and this complex appears to be stable against coordination with strong donor molecules. Publisher PDF

Hydroalumination of cyanamides 1 with di(isobutyl)aluminium hydride affords intermediate compounds 3, which have dimeric structures in the solid state with four-membered Al2N2 heterocycles and exocyclic N=C double bonds. The reactions of 3 with acyl chlorides yield N′,N′-disubstituted N-acylformamidines 5, whereas reaction with sulfonyl chlorides give the corresponding N-sulfonylformamidines 7. In contrast, carbodiimides 8 react with dialkylaluminium hydrides R2AlH (R = tBu, iBu) to give compounds 9 in which one C=N bond of the carbodiimide is reduced to form an amidinate ligand and a second molecule of the hydride is coordinated through an Al–N and an Al–H–Al bond. Treatment of 9 with acyl chlorides yields N,N′-disubstituted N-acylformamidines 10, whereas reaction with sulfonyl chlorides gives the corresponding N-sulfonylformamidines 11.

The synthesis and characterisation of two aluminium diphosphamethanide complexes, [Al(tBu)2 {κ(2) P,P'-Mes*PCHPMes*}] (3) and [Al(C6 F5 )2 {κ(2) P,P'-Mes*PCHPMes*}] (4), and the silylated analogue, Mes*PCHP(SiMe3 )Mes* (5), are reported. The aluminium complexes feature four-membered PCPAl core structures consisting of diphosphaallyl ligands. The silylated phosphine 5 was found to be a valuable precursor for the synthesis of 4 as it cleanly reacts with the diaryl aluminium chloride [(C6 F5 )2 AlCl]2 . The aluminium complex 3 reacts with molecular dihydrogen at room temperature under formation of the acyclic σ(2) λ(3) ,σ(3) λ(3) -diphosphine Mes*PCHP(H)Mes* and the corresponding dialkyl aluminium hydride [tBu2 AlH]3 . Thus, 3 belongs to the family of so-called hidden frustrated Lewis pairs.

In dieser Arbeit wird die Synthese und Charakterisierung neuer Boranate und Hydridoboranate von Aminoaluminiumverbindungen der Form [X(BH4)AlNRR‘]2 (X=H, BH4, R=Me, Et, iPr, tBu, R‘=Me, Et, iPr, H) sowie deren fast ausschließlich chloridhaltigen Vorläufermolekülen der Form [XYAlNRR‘]2 (X=H, Cl, Y=H, Cl, R=Me, Et, iPr, tBu, R‘=Me, Et, iPr, H) beschrieben. Lewis-Säure und Lewis-Base reagieren in Eliminierungsreaktionen, was zur Bildung einer kovalenten Bindung zwischen Aluminium und Stickstoff führt und die Bildung von Oligomeren zum Ausgleich des Elektronenmangels am Aluminium zur Folge hat. Für diese Reaktionen können somit nur sekundäre und primäre Amine oder deren Alkalisalze eingesetzt werden. Die Verbindung [H(BH4)AlNEt2]2 ist die erste Hydridoboranatverbindung eines Aluminiumamids, dessen Molekülstruktur beschrieben wird. Die erhaltenen Verbindungen wurden mit spektroskopischen Methoden und Röntgenstrukturbestimmung charakterisiert und auf ihr Potential zum Einsatz in der chemischen Gasphasenabscheidung (CVD) untersucht. Von einigen Verbindungen wurden mittels CVD dünne Schichten auf Metall- und Glassubstraten erhalten, deren Oberflächen mit REM und Zusammensetzung mit EDX, XRD und XPS analysiert wurden. Die Charakterisierung ergab, dass die Schichten wahrscheinlich aus Aluminium und Aluminiumoxid bestehen. In this work the synthesis and characterization of new boranates and hydrido boranates of aluminium compounds with the formula [X(BH4)AlNRR‘]2 (X=H, BH4, R=Me, Et, iPr, tBu, R‘=Me, Et, iPr, H) as well as their almost exclusively chloride containing precursor molecules with the formula [XYAlNRR‘]2 (X=H, Cl, Y=H, Cl, R=Me, Et, iPr, tBu, R‘=Me, Et, iPr, H) is described. Lewis acid and Lewis base react in elimination reactions that lead to a covalent bonding between aluminium and nitrogen and causes the building of oligomers to compensate the electron deficit at the aluminium. For this kind of reactions only secondary and primary amines or their alkaline salts can be used. The compound [H(BH4)AlNEt2]2 is the first hydrido boranate of an aluminiumamide whose molecular structure is described. The obtained compounds were analyzed with spectroscopic methods and x-ray diffraction and tested for their potential to be used in chemical vapor deposition (CVD). Thin layers of several compounds were obtained via CVD on metal and glass substrates whose surfaces were analyzed with REM and whose composition was identified with EDX, XRD and XPS. The characterization showed that the layers probably consist of aluminium and aluminiumoxide.

The effect of additives and mechanochemical processing at low temperature on β-AlD 3 has been studied. β-AlD 3 synthesized by wet chemistry was mixed with selected fluorides and cryomilled. Investigations of the fractions of α-, α′- and β-AlD 3 in the samples show that the additive and cryomilling affect the ratio of the polymorphs. Addition of AlF 3 leads to the highest ratio of α-AlD 3 , while addition of TiF 3 leads to full decomposition to Al. Formation of α′-AlD 3 during milling with NaF or MgF 2 is observed. The presence of fluorides in the synthesis of alane by cryomilling showed no notable impact on the ratios of the alane polymorphs compared to cryomilling without additives.

Pentamethylcyclopentadienyl iridium dihydride complexes [Cp*Ir(H) 2 (PR 3 )]; (PR 3 = PPh 2 Me, PTA) were prepared by reaction of [Cp*IrCl 2 (PPh 2 Me)] and [Cp*IrCl 2 (PTA)], respectively, with an excess of sodium bis(2-methoxyethoxy)aluminium hydride (Red-Al). Protonation of the dihydride [Cp*Ir(H) 2 (PPh 2 Me)] with HBF 4 ·Et 2 O at low temperature gave the classical trihydride complex [Cp*Ir(H) 3 (PPh 2 Me)]BF 4 that displays quantum mechanical exchange coupling. Reaction of [Cp*IrCl 2 (PPh 2 Me)] with CO gave the half-sandwich iridium carbonyl compound [Cp*IrCl(CO)(PPh 2 Me)]Cl which, by reaction with NaBPh 4 , yielded yellow microcrystals of [Cp*IrCl(PPh 2 Me)(CO)]BPh 4 adequate for X-ray diffraction analysis.

Aluminium hydride particles were loaded for the first time in a ZIF-8 structure by the solution infiltration method using dimethylethylamine alane [AlH3:NMe2Et] as a precursor. The infiltrated aluminium hydride is present within ZIF-8 pores preserving the zeolitic structure, as shown by various advanced analytical techniques.

A series of dimeric aluminium compounds containing substituted bidentate dianionic pyrrolyl ligands have been synthesized and their reactivity and application in the ring-opening polymerization of ϵ-caprolactone have been studied. The reactions of [{C4H3N(2-CH2NtBu)}AlH]2 (1) with 2 equiv. of 1-indanone and 9-fluorenone in dichloromethane generated [{C4H3N(2-CH2NtBu)}Al(μ-OC9H9)]2 (2) and [{C4H3N(2-CH2NtBu)}Al{μ-OCH(C12H8)}]2 (3), respectively, by hydroalumination. Similarly, the reactions of 1 with 2 equiv. of 2-cyclohexen-1-one, 1-(2,4,6-trimethylphenyl)-1-ethanone, benzophenone, and 1,1-diphenylacetone in dichloromethane afforded NtBu-bridged dialuminium compounds 4–7, [{C4H3N(2-CH2NtBu)}Al(OR)]2 [4, R = C6H9; 5, R = CH(Me)(C6H2-2,4,6-Me3); 6, R = CHPh2; 7, R = CH(Me)(CHPh2)] by insertion. A similar insertion occurred when 1 was treated with 2 equiv. of 2,4-pentandione and dibenzoylmethane in dichloromethane to yield NtBu-bridged dioxylate aluminium dimeric compounds 8 and 9, respectively. The Al atoms in compounds 2 and 4–7 possess a distorted tetrahedral geometry whereas the Al atoms in 8 and 9 have a square-pyramidal environment. All the compounds have been well characterized by NMR spectroscopy and compounds 2 and 4–9 in the solid state were subjected to X-ray diffraction analysis. A study of the polymerization of ϵ-caprolactone revealed that the activity of the Al complexes is largely reliant on the steric nature of the substituents of their alkoxide groups.

The possibility of changing the thermodynamic properties of AlH3, alane, by fluorine anion substitution has been investigated by experimental measurements, ab initio calculations and thermodynamic modelling. No solid solution phases are observed experimentally. In accordance to this the calculations give a positive free energy of mixing for all compositions, showing that a mixed phase is not thermodynamically favourable. Thus fluorine anion substitution does not seem feasible for the alane system.

By substituting Si − with (Al–H) − in trigonal BaSi 2 , a series of hydrides has been synthesized with compositions BaAl 2− x Si x H 2− x (0.4 x 2 and BaAl 2 H 2 are conductors whereas the intermediate BaAlSiH is a semiconductor. The cell parameters for the trigonal cell vary linearly as a function of the Si − /(Al–H) − substitution in this MgB 2 related structure type, opening up the possibility of continuously tunable electric properties.

Hydrogen desorption energies are considered an important factor in the selection of hydrogen storage materials. Among metal hydrides, aluminum hydride seems to be a promising material for hydrogen storage. We report the theoretical calculations of the hydrogen desorption energies of AlnH3n (n=1, 2, 3…) clusters based on Density Functional Theory (DFT). Except for very small clusters, desorption energy is seen to steadily decrease with cluster size n and reach a value of 0.19 eV per H2 for n=20, showing that for large cluster sizes approximating bulk behavior, aluminum hydride tends to be unstable. But AlnH3n clusters of sizes n=8–16 have desorption energies in the range 0.6–0.4 eV per H2, which is suitable for hydrogen storage application.