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 100 % 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

Potassium-Catalyzed Hydrosilylation of Activated Olefins: Evidence for a Silyl Migration Mechanism

The alkali-metal silyl [K­(L)­SiPh₃] (<b>1</b>; L = 18-crown-6 ether) catalyzed the hydrosilylation of activated C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 1,1′-diphenylethylene and the kinetic isotope effect of <i>k</i>_H/<i>k</i>_D = 3.1 indicate that a silyl migration mechanism is operative

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 C–C double bonds efficiently and regioselectively

Formation of a Cationic Calcium Hydride Cluster with a “Naked” Triphenylsilyl Anion by Hydrogenolysis of Bis(triphenylsilyl)calcium

Protonolysis of bis­(triphenylsilyl)­calcium [Ca­(SiPh₃)₂(THF)₄] (<b>1</b>; THF = tetrahydrofuran) with the NNNN-type macrocyclic amido triamine (Me₃TACD)H (TACD = 1,4,7-triazacyclododecane) gave the heteroleptic calcium complex [Ca­(Me₃TACD)­SiPh₃] (<b>2</b>) in quantitative yield. Hydrogenolysis of <b>2</b> gave the cationic tricalcium dihydride cluster [Ca₃H₂(Me₃TACD)₃]⁺(SiPh₃)⁻·2THF (<b>4a</b>) in high yield with concomitant formation of HSiPh₃. In the crystal, <b>4a</b> consists of a cluster cation and a free triphenylsilyl anion. ¹H NMR spectroscopy and deuterium labeling experiments confirmed the selective cleavage of dihydrogen by the highly polar Ca–Si bond in <b>1</b>