Lisa Rosenberg

Dehydrogenative coupling of primary alkyl silanes using Wilkinson's catalyst

Abstract Primary alkyl silanes (RSiH3, where R=n-C12H25 or n-C8H17) undergo dehydrogenative coupling in the presence of (Ph3P)3RhCl (1) to give oligomeric products. 29Si{1H}-NMR and gel permeation chromatography suggest that chains of up to 5–6 silicons are forming in these reactions. Variations in product distributions observed for these two substrates, of supposedly comparable SiH reactivity, may be correlated with the relative rates of departure of hydrogen gas from the reaction mixtures. The sensitivity of this system to H2(g) concentrations may ultimately allow control over specific chain lengths formed.

Silane-Controlled Diastereoselectivity in the Tris(pentafluorophenyl)borane-Catalyzed Reduction of α-Diketones to Silyl-Protected 1,2-Diols

B(C(6)F(5))(3)-catalyzed bis(hydrosilylation) of alpha-diketones can give high diastereomeric excess of either meso/anti (small silanes and disilane reagents) or dl/syn (bulky silanes) silyl-protected 1,2-diols. This easily tuned diastereoselectivity is rationalized based on the classic Felkin-Anh model applied to a mechanism relying on Si-H abstraction by the electrophilic borane reagent.

Concerted [2+2] Cycloaddition of Alkenes to a Ruthenium–Phosphorus Double Bond

We recently described a terminal phosphido complex of ruthenium containing a Ru=PR2 p bond, and demonstrated its high activity in 1,2-addition reactions of polar and nonpolar substrates. Herein we report the [2+2] cycloaddition reactions of this planar phosphido complex with both activated and simple alkenes to yield metallaphosphacyclobutanes, and we provide evidence for a concerted cycloaddition pathway in these P C bond-forming reactions (Scheme 1a). Metal-mediated P C bond-forming reactions

Semiconductors: spray-on silicon.

Reports of the death of silicon electronics may well have been exaggerated. A technique that allows the deposition of silicon films from solution could harbinger the era of the inkjet-printed circuit.Semiconductor solutionsThe manufacture of silicon semiconductor devices involves complicated photolithography and expensive machinery, so many researchers are seeking alternative semiconductor materials that can be handled by simple processes such as spin-coating or printing. Organic semiconductors are the most promising candidates but they still lack performance and reliability. Shimoda et al. have taken a different approach, printing a silicon transistor itself, not a substitute. They successfully fabricated polycrystalline silicon transistors by spin-coating a novel liquid precursor. This solution-based approach can also be adapted for ‘ink-jet’ printing of transistors.

Tuning “kappticity” of tripodal ligands

The synthesis and structural characterization of a series of tripodal tris(phosphine) ligands, containing SiMe2 elbow groups, is described. The significant steric congestion in these ligands, due to the silylmethyl substituents, is manifest both in the solid-state structures and in the solution NMR spectra of the free ligands. Variable temperature 1H{31P} NMR studies of one of the ligands, CH3C(SiMe2PEt2)3 (4b) gave an estimated barrier to rotation around the Si-Capical bonds of approximately 10.4 kcal mol(-1). Octahedral kappa2- and kappa3-molybdenum complexes of these ligands also demonstrate the impact of the additional bulk imparted by the SiMe2 substituents, and the high Lewis basicity of these phosphines, with subtle changes at the apical and phosphine substituents changing the overall coordination chemistry observed.