Latent ruthenium carbene complexes with six-membered N- and S-chelate rings

New ruthenium carbene complexes with chelating N- and S-benzylidene ligands were synthesized by the reactions of second- and third-generation Grubbs catalysts with ortho-vinylbenzyl-substituted amines or sulfides. These complexes were shown to exhibit catalytic activity in ring-opening metathesis polymerization and ring-closing metathesis.     

General procedure for the synthesis of ortho-vinylbenzyl-substituted amines, ethers, and sulfides

A convenient procedure has been proposed for the synthesis ortho-vinylbenzyl-substituted ethers, amines, and sulfides via reaction of o-(2-bromoethyl)benzyl bromide with various nucleophiles.     

NMR study of the dynamic behaviour of the system 2-ethylhexylsodium-2-ethylhexyllithium in heptane

Mixtures of 2-ethylhexylsodium and 2-ethylhexyllithium are studied by ¹H- and ¹³C-NMR spectroscopy in the temperature range from 20 to −50°C in hydrocarbon solutions. Characteristic temperature-dependent spectra obtained are indicative of dynamic exchange processes taking place in the system. The following activation parameters are found: ΔH^≠=31.7±2.7 kJ mol⁻¹; ΔG^≠₃₁₃=58.7±0.6 kJ mol⁻¹; ΔS^≠=−86.37±10.8 J mol⁻¹ K⁻¹. The negative value of the activation entropy indicates that the exchange proceeds through the associative mechanism. The participation in exchange reactions of aggregates, containing both sodium and lithium derivatives, is suggested.     

Effect of molecular structure on dehydrogenation in the case of C2 and C25-C9 alcohols

Summary The relative adsorption coefficients of aldehydes are a function of temperature: They fall with rise of temperature. To a first approximation, they do not depend on the chain length.     

The <Emphasis Type="Italic">R</Emphasis>-observability and <Emphasis Type="Italic">R</Emphasis>-controllability of linear differential-algebraic systems

We study the R-controllability (the controllability within the attainability set) and the R-observability of time-varying linear differential-algebraic equations (DAE). We analyze DAE under assumptions guaranteeing the existence of a structural form (which is called “equivalent”) with separated “differential” and “algebraic” subsystems. We prove that the existence of this form guarantees the solvability of the corresponding conjugate system, and construct the corresponding “equivalent form” for the conjugate DAE. We obtain conditions for the R-controllability and R-observability, in particular, in terms of controllability and observability matrices. We prove theorems that establish certain connections between these properties.     

Asymmetry of π− meson emission in nucleus-nucleus collisions as a measure of the target-to-projectile ratio of the numbers of interacting nucleons

Experimental data on the forward-backward asymmetry of π^- emission in (d,⁴He,¹²C)¹⁸¹Ta interactions atp/A=4.2 GeV/c are presented. The absolute value of the asymmetry coefficient of the inclusive π^- production in the nucleon-nucleonCMS decreases asA _p ^?0.35 with increasing atomic mass of projectile nucleus. A method of obtaining the target-to-projectile ratio of the numbers of participant nucleonsN _t /N _p through measuring the velocity of the symmetric pion emission system is proposed. It has been found that N_t/N_p～A _p ^?0.73 .