Over the past two decades, the high hydrogen content and favorable dehydrogenation conditions of multi-metallic amidoboranes have gained significant attention for their potential in hydrogen storage. Among them, Al-based complex hydrides have shown promise because of their high polarizing power, light weight, and abundant natural presence. In this work, we successfully synthesized two novel tetrahedrally coordinated Al-based amidoboranes, namely, Li[Al(BH3NHCH2CH2NHBH3)2] and Na(THF)[Al(BH3NHCH2CH2NHBH3)2], using BH3NH2CH2CH2NH2BH3 (EDAB) as a precursor. The structure of Na(THF)[Al(BH3NHCH2CH2NHBH3)2] was determined through modeling based on synchrotron powder X-ray diffraction. Additionally, the formation of the Al-N bond in Li[Al(BH3NHCH2CH2NHBH3)2] and Na(THF)[Al(BH3NHCH2CH2NHBH3)2] was confirmed with IR spectra. Na(THF)[Al(BH3NHCH2CH2NHBH3)2] is more stable in air than Li[Al(BH3NHCH2CH2NHBH3)2]. Importantly, thermal gravimetric analysis and mass spectroscopic characterization confirmed that both compounds release hydrogen without the presence of ammonia, diborane, or ethylenediamine. Our work represents the first example of Al-based amidoboranes with chelation coordination geometry, which provides an essential foundation for understanding the relationship of complex multi-metallic amidoboranes in terms of synthesis, structure, and properties.

Novel mesoporous gallosilicates with tuned hydrophobicity were synthesized through methylation of extra small XS-SiO2 silica particle via condensation with trimethoxymethylsilane CH3Si(OCH3)3 followed by impregnation with gallium (III) precursors. The structural and textural properties of the solids obtained were extensively characterized by different techniques. The synthesized catalysts displayed excellent catalytic activity in the acetalization of acetone with glycerol to produce solketal. Among all the studied catalysts, the most active catalyst, XS-10 %Me-GaLac, displayed high turnover number and significantly improved glycerol conversion which is attributed to the relatively hydrophobic surface and high amount of accessible active acid sites. The high acidity and enhanced hydrophobicity of this catalyst was generated by the incorporation of the methyl groups which allowed a homogeneous dispersion of highly active gallium species on the silica matrix before calcination. The effect of reaction time, temperature, catalyst loading and acetone to glycerol molar ratio was investigated. Furthermore, the mesoporous gallosilicate materials were truly heterogeneous without leaching gallium active sites and can be efficiently reused in successive catalytic cycles.

Novel mesoporous niobosilicate materials with a homogeneous dispersion of niobium species were synthesized via impregnation of (NH4)3[Nb(O2)2(edtaO2)]center dot H2O center dot H2O2 on different hydrophilic surfaces of porous siliceous supports: extra small silica nanoparticles (XS-SiO2) and silica nanotubes (NTs-SiO2) bearing three different Si/Nb molar ratios of 74, 37 and 18. The Nb-silica catalysts obtained were calcined at 600 degrees C and then fully characterized by different physico-chemical techniques. The niobium precursor was found to be successfully loaded on the two silica support surfaces without noticeable modification of the silicate structural integrity. The Nbcontaining catalysts were applied as active and selective heterogeneous catalysts for acid-catalyzed condensation of glycerol with acetone yielding solketal (2,2-dimethyl-1,3-dioxolane-4-methanol). The catalytic performance of these materials is ascribed to the enhanced accessibility of their active sites given by their morphology and to the suitable combination of acid sites. Moreover, no leaching of active sites was evidenced and the catalyst reusability studies indicated that the Nb-XS-74 and Nb-NTs-74 catalysts were successfully recyclable and highly stable in the acetalization of glycerol. The robustness and stability of the mesoporous Nb-silicate materials were also supported via characterization of the spent catalysts after the fifth recycling.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Over the last 10 years, hydrogen-rich compounds based on five-membered boron–nitrogen chain anions have attracted attention as potential hydrogen storage candidates. In this work, we synthesized Na[BH3(CH3NH)BH2(CH3NH)BH3] through a simple mechanochemical approach. The structure of this compound, obtained through synchrotron powder X-ray diffraction, is presented here for the first time. Its hydrogen release properties were studied by thermogravimetric analysis and mass spectrometry. It is shown here that Na[BH3(CH3NH)BH2(CH3NH)BH3], on the contrary of its parent counterpart, Na[BH3NH2BH2NH2BH3], is able to release up to 4.6 wt.% of pure hydrogen below 150 °C. These results demonstrate that the introduction of a methyl group on nitrogen atom may be a good strategy to efficiently suppress the release of commonly encountered undesired gaseous by-products during the thermal dehydrogenation of B-N-H compounds.

The present study further explores the behavior of polyoxometalate-based hybrid compounds as catalysts for liquid-phase cyclooctene epoxidation with H2O2. Precisely, it unveils the nature of the relevant active species derived from the hybrid based on Keggin polyoxometalate (POM) and bipyridines (bpy) of formula (2,2'-Hbpy)3[PW12O40] (1). Whereas (i) it is generally accepted that the catalytic oxidation of organic substrates by H2O2 involving Keggin HPAs proceeds via an oxygen transfer route from a peroxo intermediate and (ii) the catalytically active peroxo species is commonly postulated to be the polyperoxotungstate {PO4[W(O)(O2)2]4}3- complex (PW4), we show that the studied epoxidation reaction seems to be more sophisticated than commonly reported. During the catalytic epoxidation, 1 underwent a partial transformation into two oxidized species, 2 and 3. Compound 3 corresponding to 2,2'-bipyridinium oxodiperoxotungstate of formula [WO(O2)2(2,2'-bpy)] was shown to be the main species responsible for the selective epoxidation of cyclooctene since 2 (in which the POM is associated with a protonated mono-N-oxide derivative of 2,2'-bpy of formula (2,2'-HbpyO)3[PW12O40]) exhibited no activity. The structures of 1, 2, and 3 were solved by single-crystal X-ray diffraction and were independently synthesized. The speciation of 1 was monitored under catalytic conditions by 1H and 1H DOSY NMR spectroscopies, where the formation in situ of 2 and 3 was revealed. A reaction mechanism is proposed that highlights the pivotal, yet often underestimated, role of H2O2 in the reached catalytic performances. The active species responsible for the oxygen transfer to cyclooctene is a hydroperoxide intermediate species that is formed by the interaction between the anionic structure of the catalyst and H2O2. The latter operates as a "conservative agent" whose presence in the catalytic system is required to prevent the catalysts from deactivating irreversibly.

Na[Al(CH3NHBH3)4] and an intermediate Na[AlH(CH3NHBH3)3] were synthesized by ball milling. Na[Al(CH3NHBH3)4] + 12NaH/6NaNH2 released pure hydrogen at moderate temperatures, making this and similar systems interesting candidates for H-storage.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

A thorough investigation of two novel hybrid materials, namely, (2,2'-Hbpy)3[PW12O40] and (4,4'-H2bpy)1.5[PW12O40]·1.5H2O built from Keggin phosphotungstic acid (PTA) and bipyridine, describes the impact of bipyridine isomers in their formation and physicochemical properties. The hybrids' formation was confirmed by powder X-ray diffraction, while infrared spectroscopy (IR) proved the polyoxometalate (POM) structural preservation. The stoichiometric composition and thermal stability of the hybrids were solved by thermogravimetric analysis-mass spectrometry, which also revealed newly acquired hydrophobic properties. Raman and IR spectroscopies demonstrated that the POM skeleton units in both hybrids were distorted compared to the POM in PTA, which induced a decrease of their reduction potentials as observed by diffuse reflectance ultraviolet-visible spectroscopy (DR-UV-vis). The hybrids' acidity was assessed by ammonia temperature-programmed desorption, which showed no remaining acid sites compared to the strong acidic character of the pristine PTA. The properties of the hybrids were tested in the epoxidation of cyclooctene in the presence of H2O2. The reaction was boosted when the hybrids were pre-activated with H2O2.

Herein, we report the preparation of four compounds obtained by the reaction of H3PW12O40/H3PO4/H2O2 with 2,2'-bpy (a-22) or 4,4'-bpy (a-44) and H3PW12O40/H2O2 with 2,2'-bpy (b-22) or 4,4'-bpy (b-44) for the catalytic epoxidation of cyclooctene with H2O2 under monophasic conditions. The anions of the four compounds are composed of oxodiperoxotungstate WO(O2)2 moieties and their overall anionic structures are less condensed than the pristine [PW12O40]3- polyoxometalate (PW12) precursor (Raman and IR spectroscopies). The peroxo anions and bipyridine interact in a way differing from one bpy isomer to the other. Isomer 4,4'-bpy interacts electrostatically with the peroxo species and 2,2'-bpy in a coordinative mode. Compounds synthesized with isomer 2,2'-bpy (a-22 and b-22) are more epoxidation-active than those containing 4,4'-bpy (a-44 and b-44). Compounds a-22 and b-22 share the same structure (PXRD), but a-22 exhibits substantially better catalytic activity. This superior catalytic efficiency is associated to the presence of phosphatooxoperoxotungstates PWn (n = 1; 2; 3; 4) species with high n value (namely PW4 > PW3 >> PW2) (31P NMR and Raman spectroscopies). The PWn species are produced before reaction with bipyridine as a result of the degradation of PW12 with H2O2 which, under the employed conditions, is complete after 30 min. In the aqueous solution, the PWn species are present in different concentrations and coexist in a fast-dynamic equilibrium. Under the operated catalytic conditions, our materials outperform the homogeneous benchmark catalyst of Venturello ((C6H13)4N+)3[PW4O24]3-) which shows poor activity. The most active a-22 and b-22 catalysts are partially dissolved in the liquid medium, but they precipitate as the epoxide builds in the reaction medium, allowing for potential catalyst separation and reuse. It is revealed that H2O2 is required not only to generate epoxidation activity, but to preserve the structure of the catalyst, since without it, the structural damaged appears irreversible.

Bimetallic carbon-supported PdBi catalysts were prepared by grafting. To do so a soluble complex of bismuth with exchangeable O-donor ligands was selected, and the carbon support was functionalized to increase the number of surface functions. The grafting procedure was carried out by contacting the various supports with solutions of Pd and/or Bi complexes, to allow ligand exchange reactions to take place between the complexes and the surface O-groups. The grafted fragments were then activated into carbon-supported nanoparticles, which were characterized to unravel the impact of grafting experimental variables on the physico-chemical characteristics of the materials obtained. The PdBi/C catalysts were finally tested in the archetypal glucose selective oxidation reaction, to assess the impact of those characteristics on the catalytic performance. It was found that simultaneous grafting gave larger nanoparticles than consecutive grafting, while higher number of stable surface functions allowed to obtain small and nicely distributed bimetallic nanoparticles. However, the surface functions were found to be deleterious for the catalytic activity, and the placement of the Bi promoter with respect to Pd active phase was identified as another key parameter for the activity, with grafting allowing to compare neatly samples where Bi is underneath, above or beside Pd.

Two mesoporous gallosilicates with extra‐small particle size were synthesized via wet impregnation starting from lactate or citrate‐type Ga(III) precursors. The structural and textural properties of the materials were extensively characterized by different techniques. Both materials consist of nanosized particles and display a remarkably high surface area and a pore size distribution typical of mesoporous MCM‐41‐like materials. The two solids were tested as catalysts in acetalization of glycerol with acetone to produce solketal (2,2‐dimethyl‐1,3‐dioxolane‐4‐methanol). Both catalysts displayed excellent performances and achieved higher turnover numbers compared to other Ga‐silicates reported in literature. The outstanding activity of these catalysts is attributed to the combination of acidity, large specific surface area as well as to the full accessibility of the active sites as consequence of the impregnation procedure. The best catalysts are truly heterogeneous with absence of Ga leaching and reusable in successive catalytic cycles after thermal treatment without significant deterioration of the catalytic performance.

The surface coordination chemistry of Pd complexes on alumina has been studied in the framework of synthesizing Pd/-Al2O3 catalytic materials. Two methodologies were explored: the direct grafting of Pd complexes on hydroxyl functions present at the alumina surface and the anchoring of the precursors via amine-bearing silanes previously grafted on the support. Suitable conditions to graft and anchor Pd complexes on alumina surface were found and experimental proofs of grafting and anchoring processes are provided. The results show that covalent grafting indeed took place for samples prepared in acetonitrile with [Pd(CF3CO2)(2)(bipy)] and [PdCl2(PhCN)(2)] complexes or with [Pd(OAc)(2)] and [Pd(CF3CO2)(2)] in acetone. The anchoring was successful for catalysts prepared in acetone with 1 wt.% of [Pd(CF3CO2)(2)] loading. Grafting and anchoring were found to stabilize palladium in its Pd(II) oxidation state. This has an adverse effect on the activation step that should lead to reduction of the complex to give the metallic catalytic supported active phase.

The Cover Feature shows novel aluminum-based metal borohydrides as high-capacity hydrogen storage materials. The conversion of hydrogen-rich but explosive liquid Al(BH4)3 to a more stable family of mixed-cation M[Al(BH4)4] (M=alkali metal or NH4+) solid borohydrides opens new doors for energy storage. Their thermal decomposition properties show diverse behaviors and provides this family of solids with convenient and versatile properties, putting aluminum borohydride chemistry in the mainstream of the hydrogen storage research. More information can be found in the Full Paper by Dovgaliuk et al. on page 4725 in Issue 23, 2017 (DOI: 10.1002/cssc.201701629).

Metal borohydrides are intensively researched as high-capacity hydrogen storage materials. Aluminum is a cheap, light, and abundant element and Al3+ can serve as a template for reversible dehydrogenation. However, Al(BH4 )3 , containing 16.9 wt % of hydrogen, has a low boiling point, is explosive on air and has poor storage stability. A new family of mixed-cation borohydrides M[Al(BH4 )4 ], which are all solid under ambient conditions, show diverse thermal decomposition behaviors: Al(BH4 )3 is released for M=Li+ or Na+ , whereas heavier derivatives evolve hydrogen and diborane. NH4 [Al(BH4 )4 ], containing both protic and hydridic hydrogen, has the lowest decomposition temperature of 35 °C and yields Al(BH4 )3 ⋅NHBH and hydrogen. The decomposition temperatures, correlated with the cations' ionic potential, show that M[Al(BH4 )4 ] species are in the most practical stability window. This family of solids, with convenient and versatile properties, puts aluminum borohydride chemistry in the mainstream of hydrogen storage research, for example, for the development of reactive hydride composites with increased hydrogen content.

Nanostructured hybrid materials made of guest ions and a self-assembled copolymer were used as precursors for the preparation of NiMo-based catalysts. The hybrids were calcined in air and the recovered materials were characterized and tested in propane oxidative dehydrogenation. A 6-fold improvement of the yield to propene is obtained as compared with classically prepared catalysts. The exothermic degradation profile of the copolymer is the key point of our approach as it allows to prepare a porous beta-NiMoO4, namely the phase particularly desired for its superior propene selectivity. More precisely, the polar backbone and the aliphatic side chains of the copolymer burn at different temperatures. The former ignites at moderate temperatures and initiates the early crystallization of beta-NiMoO4. Occurring at higher temperature, the decomposition of the aliphatic part then induces the formation of mesopores. A beta-NiMoO4 can thus be prepared at moderate temperatures whereas elevated calcination temperatures (>650 degrees C) are usually required. This peculiar behavior enables to prevent the texture of NiMoO4 from sintering and to maintain at high levels its mesoporosity, specific area and thus catalytic activity. At the end, the use of our tailor designed copolymer template allows reaching the remarkably high propene yields obtained. (C) 2017 Elsevier Inc. All rights reserved.

Nanostructured hybrid materials made of guest ions and a polyampholytic self-assembled copolymer are here synthesized. Their lamellar organization results from hydrophobic interactions between the copolymer alkyl side chains. Longer side chains improve the organization of hybrids what makes them more attractive to be used as a template for the preparation of sophisticated catalysts. However, they also enhance the hydrophobicity of the copolymer what complicates the synthesis of such hybrids. Dodecyl side chains appear as a compromise that enables to prepare well organized hybrids without sacrificing the copolymer capacity to link ions.

Detailed XPS experimental X-ray photoelectron spectroscopy (XPS) was performed on a Kratos Axis Ultra spectrometer (Kratos Analytical) equipped with a monochromatized aluminum X-ray source powered at 10 mA and 15 kV. The powder samples were gently pressed with a spatula on an isolating double sided adhesive tape fixed on a polyacetal polymer piece. The pressure in the analysis chamber was about 10-6 Pa. The angle between the normal to the sample surface and the direction of photoelectron collection was 0°. Analyses were performed in the hybrid lens mode which is a combination of magnetic and electrostatic lenses. The slot aperture was used, the iris drive position was set at 0.5 and the analyzed area was 700 μm x 300 μm. The pass energy of the hemispherical analyzer was set at 160 and 40 eV for the survey scan and the narrow scans respectively. In such conditions, the full width at half maximum (FWHM) of the Ag3d5/2 peak of a standard silver sample was about 0.9 eV. The charge stabilization was achieved by means of an electron source co-axially mounted to the electrostatic lens column. A charge balance plate (-4 V) was used to reflect electrons back towards the sample. The magnetic field of the immersion lens placed below the sample acted as a guide path for the low energy electrons returning to the sample. The electron source was operated under a filament current of 0.16 A and a bias of -1.2 eV.

Attempts to synthesize Au–Pd heterometallic compounds from homonuclear palladium or gold complexes, [Pd(PtBu 2 ) 2 ] and [Au(PPh 3 )Cl] in a tetrahydrofuran (THF) solution under a CO atmosphere resulted in a homonuclear Pd cluster, namely pentakis(μ-carbonyl-κ 2 C : C )tetrakis(triphenylphosphane-κ P )tetrapalladium(5 Pd — Pd ) tetrahydrofuran disolvate, [Pd 4 (CO) 5 (C 18 H 15 P) 4 ]·2C 4 H 8 O. The complex molecule lies on a twofold rotation axis. The crystal structure is described in relation to the CH 2 Cl 2 solvate previously determined by our group [Willocq et al. (2011). Inorg. Chim. Acta , 373 , 233–242], and in particular to the desolvated structure [Feltham et al. (1985). Inorg. Chem. 24 , 1503–1510]. It is assumed that the title compound transforms into the latter structure, upon gradual loss of solvent molecules. In the title compound, the symmetry-unique THF solvent molecule is linked to the complex molecule by a weak C—H...O hydrogen bond. Contributions of disordered solvent molecules to the diffraction intensities, most likely associated with methanol, were removed with the SQUEEZE [Spek (2015). Acta Cryst. C 71 , 9–18] algorithm.