17 research outputs found
Investigation of commercial graphenes
For graphene to achieve its full scientific and commercial potential, reliable mass production of the material on the multi-tonne scale is essential. We have investigated five samples of graphene obtained from commercial sources that state they can supply the product on the tonne scale per annum. From electron microscopy at the micrometre to the nanometre scale, and neutron vibrational spectroscopy, we find that none of the materials examined were 100â% isolated graphene sheets. In all cases, there was a substantial content of graphite-like material. The samples exhibited varying oxygen contents, this could be present as carboxylic acid (although other oxygenates, quinones, phenols may also be present) or water. We emphasise that INS spectroscopy is particularly useful for the investigation of inorganic materials that will be used commercially: it provides atomic scale information from macroscopic (10's of g) amounts of sample, thus ensuring that the results are truly representative
Alkali and alkaline earth metal silyl complexes : synthesis, reactivity and application in homogeneous catalysis
Potassium-Catalyzed Hydrosilylation of Activated Olefins: Evidence for a Silyl Migration Mechanism
The
alkali-metal silyl [KÂ(L)ÂSiPh<sub>3</sub>] (<b>1</b>;
L = 18-crown-6 ether) catalyzed the hydrosilylation of activated Cî»C
double bonds. Isolation and characterization of an addition product
is in agreement with the anti-Markovnikov selectivity. Second-order
kinetics for the hydrosilylation of 1,1âČ-diphenylethylene and
the kinetic isotope effect of <i>k</i><sub>H</sub>/<i>k</i><sub>D</sub> = 3.1 indicate that a silyl migration mechanism
is operative
Calcium-Mediated Dearomatization, C[BOND]H Bond Activation, and Allylation of Alkylated and Benzannulated Pyridine Derivatives
Crown ether adducts of light alkali metal triphenylsilyls: synthesis, structure and hydrosilylation catalysis
Molekulares Calciumhydrid: Dicalciumtrihydrid-Kation, stabilisiert durch einen neutralen makrocyclischen NNNN-Liganden
Hydrosilylation catalysis by an earth alkaline metal silyl: synthesis, characterization, and reactivity of bis(triphenylsilyl)calcium
International audienceBis(triphenylsilyl)calcium [Ca(SiPh3)2(thf)] obtained in high yield as a crystalline ether adduct catalyzes the hydrosilylation of activated CâC double bonds efficiently and regioselectively
Silyl-Hydrosilane Exchange at a Magnesium Triphenylsilyl Complex Supported by a Cyclen-Derived NNNN-Type Macrocyclic Ligand
Formation of a Cationic Calcium Hydride Cluster with a âNakedâ Triphenylsilyl Anion by Hydrogenolysis of Bis(triphenylsilyl)calcium
Protonolysis of bisÂ(triphenylsilyl)Âcalcium
[CaÂ(SiPh<sub>3</sub>)<sub>2</sub>(THF)<sub>4</sub>] (<b>1</b>; THF = tetrahydrofuran) with the NNNN-type macrocyclic amido triamine
(Me<sub>3</sub>TACD)H (TACD = 1,4,7-triazacyclododecane) gave the
heteroleptic calcium complex [CaÂ(Me<sub>3</sub>TACD)ÂSiPh<sub>3</sub>] (<b>2</b>) in quantitative yield. Hydrogenolysis of <b>2</b> gave the cationic tricalcium dihydride cluster [Ca<sub>3</sub>H<sub>2</sub>(Me<sub>3</sub>TACD)<sub>3</sub>]<sup>+</sup>(SiPh<sub>3</sub>)<sup>â</sup>·2THF (<b>4a</b>) in high yield
with concomitant formation of HSiPh<sub>3</sub>. In the crystal, <b>4a</b> consists of a cluster cation and a free triphenylsilyl
anion. <sup>1</sup>H NMR spectroscopy and deuterium labeling experiments
confirmed the selective cleavage of dihydrogen by the highly polar
CaâSi bond in <b>1</b>