Titanium Hydride Nanoplates Enable 5 wt% of Reversible Hydrogen Storage by Sodium Alanate below 80°C

Sodium alanate (NaAlH4) with 5.6 wt% of hydrogen capacity suffers seriously from the sluggish kinetics for reversible hydrogen storage. Ti-based dopants such as TiCl4, TiCl3, TiF3, and TiO2 are prominent in enhancing the dehydrogenation kinetics and hence reducing the operation temperature. The tradeoff, however, is a considerable decrease of the reversible hydrogen capacity, which largely lowers the practical value of NaAlH4. Here, we successfully synthesized a new Ti-dopant, i.e., TiH2 as nanoplates with ~50 nm in lateral size and ~15 nm in thickness by an ultrasound-driven metathesis reaction between TiCl4 and LiH in THF with graphene as supports (denoted as NP-TiH2@G). Doping of 7 wt% NP-TiH2@G enables a full dehydrogenation of NaAlH4 at 80°C and rehydrogenation at 30°C under 100 atm H2 with a reversible hydrogen capacity of 5 wt%, superior to all literature results reported so far. This indicates that nanostructured TiH2 is much more effective than Ti-dopants in improving the hydrogen storage performance of NaAlH4. Our finding not only pushes the practical application of NaAlH4 forward greatly but also opens up new opportunities to tailor the kinetics with the minimal capacity loss.

1H NMR Analysis of the Metathesis Reaction between 1-Hexene and (E)-Anethole Using Grubbs 2nd Generation Catalyst: Effect of Reaction Conditions on (E)-1-(4-Methoxyphenyl)-1-hexene Formation and Decomposition

The metathesis of 1-hexene and (E)-anethole in the presence of Grubbs 2nd generation catalyst was monitored by in situ 1H NMR spectroscopy at different temperatures (15 °C, 25 °C, and 45 °C) and anethole mol fractions (XAnethole ≈ 0.17, 0.29, 0.5, 0.71, 0.83). Time traces confirmed the instantaneous formation of (E)-1-(4-methoxyphenyl)-1-hexene, the cross-metathesis product. A maximum concentration of (E)-1-(4-methoxyphenyl)-1-hexene is reached fairly fast (the time depending on the reaction conditions), and this is followed by a decrease in the concentration of (E)-1-(4-methoxyphenyl)-1-hexene due to secondary metathesis. The maximum concentration of (E)-1-(4-methoxyphenyl)-1-hexene was more dependent on the XAnethole than the temperature. The highest TOF (3.46 min−1) was obtained for the reaction where XAnethole was 0.16 at 45 °C. The highest concentration of the cross-metathesis product was however achieved after 6 min with an anethole mol fraction of 0.84 at 25 °C. A preliminary kinetic study indicated that the secondary metathesis reaction followed first order kinetics.

Synthesis and Reactivity of Group 12 β-Diketiminate Coordination Complexes

<p>The variable β-diketiminate ligand poses as a suitable chemical environment to explore unknown reactivity and functionality of metal centres. Variants on the β-diketiminate ligand can provide appropriate steric and electronic stabilization to synthesize a range of β-diketiminate group 12 metal complexes. This project aimed to explore various β-diketiminate ligands as appropriate ancillary ligands to derivatise group 12 element complexes and investigate their reactivity. A β-diketiminato-mercury(II) chloride, [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]HgCl, was synthesized by addition of [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]Li to mercury dichloride. Attempts to derivatise the β-diketiminato-mercury(II) chloride using salt metathesis reactions were unsuccessful with only β-diketiminate ligand degradation products being observed in the ¹H NMR. A β-diketiminato-cadmium chloride, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂]CdCl, was derivatized to a β-diketiminato-cadmium phosphanide, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂]Cd P(C₆H₁₁)₂, via a lithium dicyclohexyl phosphanide and a novel β-diketiminato-cadmium hydride, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂]CdH, via Super Hydride. Initial reactivity studies of the novel cadmium hydride with various carbodiimides yielded a β-diketiminato-homonuclear cadmium-cadmium dimer, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂Cd]₂, which formed via catalytic reduction of the cadmium hydride. Attempts to synthesize an amidinate insertion product via a salt metathesis reaction or a ligand exchange reaction proved unsuccessful but a novel cadmium amidinate, [{CH(N-C₆H₁₁)₂}₂{CH(N-C₆H₁₁)(N(H)-C₆H₁₁)}Cd], was synthesized from addition of dicyclohexyl formamidine to bis-hexamethyldisilazane cadmium. A β-diketiminato-zinc(II) bromide, [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]ZnBr, was synthesized by addition of [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]Li to zinc dibromide. The β-diketiminato-zinc(II) bromide was derivatized to a variety of complexes (including amides and phosphanides) by a salt metathesis reaction. Chalcogen addition reactions were performed from [o-C₆H₄{C(CH₃)=N-2,6-iPr₂C₆H₃}{NH(2,6-iPr₂C₆H₃)}ZnP(C₆H₁₁)₂] to produce double addition products from sulfur, selenium and tellurium. Chalcogen addition reactions from [o-C₆H₄{C(CH₃)=N-2,6-iPr₂C₆H₃}{NH(2,6-iPr₂C₆H₃)}ZnP(C₆H₅)₂] produced a double addition product for selenium and a β-diketiminato-zinc(II) tellunoite bridged dimer, [o-C₆H₄{C(CH₃)=N-2,6-iPr₂C₆H₃}{NH(2,6-iPr₂C₆H₃)}Zn]Te, from tellurium. A total of 14 compounds were characterized via X-ray diffraction. Photoluminescence studies of the β-diketiminato-zinc(II) compounds were conducted where it was proposed that an electron transfer from the lone pair on the hetero-atom influenced the quantum yield and fluorescence intensities.</p>

Synthesis and Reactivity of Group 12 β-Diketiminate Coordination Complexes

<p>The variable β-diketiminate ligand poses as a suitable chemical environment to explore unknown reactivity and functionality of metal centres. Variants on the β-diketiminate ligand can provide appropriate steric and electronic stabilization to synthesize a range of β-diketiminate group 12 metal complexes. This project aimed to explore various β-diketiminate ligands as appropriate ancillary ligands to derivatise group 12 element complexes and investigate their reactivity. A β-diketiminato-mercury(II) chloride, [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]HgCl, was synthesized by addition of [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]Li to mercury dichloride. Attempts to derivatise the β-diketiminato-mercury(II) chloride using salt metathesis reactions were unsuccessful with only β-diketiminate ligand degradation products being observed in the ¹H NMR. A β-diketiminato-cadmium chloride, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂]CdCl, was derivatized to a β-diketiminato-cadmium phosphanide, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂]Cd P(C₆H₁₁)₂, via a lithium dicyclohexyl phosphanide and a novel β-diketiminato-cadmium hydride, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂]CdH, via Super Hydride. Initial reactivity studies of the novel cadmium hydride with various carbodiimides yielded a β-diketiminato-homonuclear cadmium-cadmium dimer, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂Cd]₂, which formed via catalytic reduction of the cadmium hydride. Attempts to synthesize an amidinate insertion product via a salt metathesis reaction or a ligand exchange reaction proved unsuccessful but a novel cadmium amidinate, [{CH(N-C₆H₁₁)₂}₂{CH(N-C₆H₁₁)(N(H)-C₆H₁₁)}Cd], was synthesized from addition of dicyclohexyl formamidine to bis-hexamethyldisilazane cadmium. A β-diketiminato-zinc(II) bromide, [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]ZnBr, was synthesized by addition of [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]Li to zinc dibromide. The β-diketiminato-zinc(II) bromide was derivatized to a variety of complexes (including amides and phosphanides) by a salt metathesis reaction. Chalcogen addition reactions were performed from [o-C₆H₄{C(CH₃)=N-2,6-iPr₂C₆H₃}{NH(2,6-iPr₂C₆H₃)}ZnP(C₆H₁₁)₂] to produce double addition products from sulfur, selenium and tellurium. Chalcogen addition reactions from [o-C₆H₄{C(CH₃)=N-2,6-iPr₂C₆H₃}{NH(2,6-iPr₂C₆H₃)}ZnP(C₆H₅)₂] produced a double addition product for selenium and a β-diketiminato-zinc(II) tellunoite bridged dimer, [o-C₆H₄{C(CH₃)=N-2,6-iPr₂C₆H₃}{NH(2,6-iPr₂C₆H₃)}Zn]Te, from tellurium. A total of 14 compounds were characterized via X-ray diffraction. Photoluminescence studies of the β-diketiminato-zinc(II) compounds were conducted where it was proposed that an electron transfer from the lone pair on the hetero-atom influenced the quantum yield and fluorescence intensities.</p>

Room-Temperature Metathesis of Ethylene with 2-Butene to Propene Over MoOx-Based Catalysts: Mixed Oxides as Perspective Support Materials

We investigated the effect of supports based on ZrO2, TiO2, Al2O3, and SiO2 on the rate of propene formation in the metathesis of ethylene with 2-butene at 50 °C over Mo-containing catalysts possessing highly dispersed MoOx. Large improvements in this rate were achieved when using supports composed of mixed oxides (ZrO2–SiO2, ZrO2–PO4, TiO2–SiO2; Al2O3–SiO2) rather than of individual oxides (ZrO2, TiO2, Al2O3, SiO2). Although previous literature studies dealing with the metathesis reaction over Al2O3- or SiO2-suppported catalysts at higher temperatures suggest the importance of redox or acidic properties of supported MoOx species for catalyst activity, we were not able to establish any general direct correlation in this regard. Contrarily, the rate of propene formation can be significantly enhanced when promoting supports with an oxide promoter. We suggest that the created support lattice defects may facilitate the transformation of MoOx to Mo carbenes under reaction conditions or improve the intrinsic activity of the latter. Graphic Abstract

First total synthesis of thiocladospolide A and its C2-epimer

The first total synthesis of recently isolated thiocladospolide A (1) and its C2-epimer have been achieved in nine straightforward linear steps with 12% of overall yield. The key feature of the synthesis is the construction of the macrocyclic ring via late stage ring-closing metathesis reaction followed by alkene reduction.

Towards deeper understanding of multifaceted chemistry of magnesium alkylperoxides

Despite considerable progress in the multifaceted chemistry of non-redox-metal alkylperoxides, the knowledge about magnesium alkylperoxides is in its infancy and only started to gain momentum. Harnessing the well-defined dimeric magnesium tert-butylperoxide [(f5BDI)Mg(μ-η2:η1-OOtBu)]2 incorporating a fluorinated β-diketiminate ligand, herein, we demonstrate its transformation at ambient temperature to a spiro-type, tetranuclear magnesium alkylperoxide [(f5BDI)2Mg4(μ-OOtBu)6]. The latter compound was characterized by single-crystal X-ray diffraction and its molecular structure can formally be considered as a homoleptic magnesium tert-butylperoxide [Mg(µ-OOtBu)2]2 terminated by two monomeric magnesium tert-butylperoxides. The formation of the tetranuclear magnesium alkylperoxide not only contradicts the notion of the high instability of magnesium alkylperoxides, but also highlights that there is much to be clarified with respect to the solution behaviour of these species. Finally, we probed the reactivity of the dimeric alkylperoxide in model oxygen transfer reactions like the commonly invoked metathesis reaction with the parent alkylmagnesium and the catalytic epoxidation of trans-chalcone with tert-butylhydroperoxide as an oxidant. The results showed that the investigated system is among the most active known catalysts for the epoxidation of enones.

Synthesis and characterization of a range of antimony(I/III) N,N′-bis(2,6-diisopropylphenyl)formamidinate complexes

Formamidinatoantimony(I/III) complexes have been successfully synthesized as monomers or dimers in the solid state featuring a variety of coordination geometries and have also been comprehensively characterized. The antimony(I) formamidinate complex bis[μ-N,N′-bis(2,6-diisopropylphenyl)formamidinato]diantimony(I)(2 Sb—Sb) tetrahydrofuran heptasolvate, [Sb2(C25H35N2)2]·7C4H8O or [Sb2(DippForm)2]·7THF, (1), was obtained by a metathesis reaction between sodium bis(trimethylsilyl)amide [NaN(SiMe3)2] and N,N′-bis(2,6-diisopropylphenyl)formamidine (DippFormH), followed by SbCl3. A range of trivalent haloformamidinatoantimony(III) complexes, namely, bis[N,N′-bis(2,6-diisopropylphenyl)formamidinato]chloridoantimony(III), [Sb(C25H35N2)2Cl] or [Sb(DippForm)2Cl], (2), bis[N,N′-bis(2,6-diisopropylphenyl)formamidinato]bromidoantimony(III), [SbBr(C25H35N2)2] or [SbBr(DippForm)2], (3), bis[N,N′-bis(2,6-diisopropylphenyl)formamidinato]iodidoantimony(III), [Sb(C25H35N2)2I] or [Sb(DippForm)2I], (4), [N,N′-bis(2,6-diisopropylphenyl)formamidinato]dibromidoantimony(III), [SbBr2(C25H35N2)] or [SbBr2(DippForm)], (5), and [N,N′-bis(2,6-diisopropylphenyl)formamidinato]diiodidoantimony(III), [Sb(C25H35N2)I2] or [Sb(DippForm)I2], (6), were also synthesized by adding DippFormH and MN(SiMe3)2 (M = Li or Na) to the corresponding antimony halides SbX 3 (X = Cl, Br or I) in differing ratios. The complexes were all stable to rearrangement.