Synthetic Pathways to Hydrogen-Rich Polysilylated Arenes from Trialkoxysilanes and Other Precursors

Negative Poisson's ratio and high-mobility transport anisotropy in SiC6 siligraphene

The diverse forms of silicon carbides lead to versatile properties, but an auxetic allotrope at zero pressure has never been reported. Here, using first-principles calculations we propose a two-dimensional (2D) auxetic silicon carbide material, namely SiC₆ siligraphene. The plausibility of the SiC₆ siligraphene is verified by the low formation energy, positive phonon spectrum and high mechanical stability. The unique framework of sp² carbon and sp³ silicon atoms leads to unusual in-plane negative Poisson's ratios and electronic properties superior to both graphene and silicene. SiC₆ siligraphene possesses a natural band gap of 0.73 eV and a high carrier mobility. The theoretical mobility in the order of 10⁴ cm² V^-1 s^-1 for electrons along the [1[combining macron]10] direction is comparable to the hole mobility in black phosphorene, whereas the hole transport along the [110] direction is blocked. Both the electronic band structure and carrier mobility of the SiC₆ siligraphene can be tuned by applying external strain. A possible synthetic route is also proposed. The exotic properties make SiC₆ siligraphene a versatile and promising 2D material for applications in nanomechanics and nanoelectronics.

Current advances in the catalytic conversion of carbon dioxide by molecular catalysts: an update

Recent advances (2015–) in the catalytic conversion of CO₂ by metal-based and metal-free systems are discussed.

Hydrodealkoxylation reactions of silyl ligands at platinum: reactivity of SiH₃ and SiH₂Me complexes

The platinum(ii) complex [Pt(H)2(dcpe)] (; dcpe = 1,2-bis(dicyclohexylphosphino)ethane) reacts with an excess of the dialkoxymethylsilanes (HSiMe(OR)2; R = Me, Et) to give the bis(silyl) complex [Pt(SiH2Me)2(dcpe)] () and trialkoxymethylsilanes by hydrodealkoxylation reactions. These rearrangements of the silyl ligands involve Si-O bond activations. The exchange of the alkoxy moieties against silicon-bound hydrogen atoms occurs stepwise. The intermediate complexes [Pt(H){SiMe(OEt)2}(dcpe)] (), [Pt{SiMe(OEt)2}2(dcpe)] (), [Pt{SiHMe(OEt)}2(dcpe)] () and [Pt{SiHMe(OMe)}2(dcpe)] () were detected. Treatment of the complex with an excess of dichloromethylsilane yields the bis(silyl) complex [Pt(SiMeCl2)2(dcpe)] (). The hydrido silyl complex [Pt(H)(SiMeCl2)(dcpe)] () was identified as an intermediate. The reactions of the complexes [Pt(SiH3)2(dcpe)] () and [Pt(SiH2Me)2(dcpe)] () with iodomethane lead to a transfer of the SiH3 and SiH2Me ligands. Methylsilane and dimethylsilane, respectively, as well as the platinum diiodo complex [Pt(I)2(dcpe)] () were identified as main products.

Organized self-assembled monolayers from organosilanes containing rigid pi-conjugated aromatic segments

The morphology of surfaces modified by pi-conjugated arylsilanes depends on various parameters such as the nature and the number of the hydrolyzable functions or the length of the aromatic segment. The grafting of phenyltrichlorosilane and phenyltrimethoxysilane leads to multilayers even when the reactions are carried out at 0 degrees C, the films obtained from phenyltrichlorosilane being much thicker than the one obtained from phenyltrimethoxysilane. A submonolayer is obtained using phenyltriethoxysilane. Whereas the trifunctional phenyltrichlorosilane forms an inhomogeneous multilayer, the difunctional phenyldichlorosilane (PhSiHCl2) and the monofunctional phenylchlorosilane (PhSiH2Cl) (the SiH bond is not reactive under these experimental conditions) deposit as dense homogeneous monolayers. For these two phenylchlorosilanes, the surface analytical data are similar except for contact angle measurements, which can be explained by a different orientation of the phenyl group at the surface. Concerning the influence of the length of the aromatic segment on the quality of the film, styryltrimethoxysilane and methylstilbenyltrimethoxysilane lead to dense monolayers indicating that adding a short group such as the vinyl group is sufficient to induce an organization between aromatic groups and to achieve a dense monolayer.