2-(Polyfluoroalkyl)chromones. 15. Transformation of 3-chloro-2-(polyfluoroalkyl)chromones into benzofuran derivatives by hydroxylamine

The reactions of 3-chloro-2-(polyfluoroalkyl)chromones with hydroxylamine in the presence of sodium acetate proceed with ring contraction to form benzofuran derivatives.     

Methoxycarbonyltrifluoromethylthioketene

A new method was developed for the synthesis of methoxycarbonyltrifluoromethylthioketene by thermal cleavage of tert-butyl 1,3,3,3-tetrafluoro-2-methoxycarbonylpropenyl sulfide in the presence of P₂O₅. This thioketene was demonstrated to exhibit high reactivity in reactions with nucleophiles as well as in ene and diene syntheses.     

Structural chemistry of titanium and aluminium bimetallic hydride complexes: IV. Molecular structures and catalytic properties of {[η5-C5(CH3)5]2Ti(μ2-H)2Al(H)(μ2-H)}2 and [η5-C5(CH3)5]2Ti(μ2-H)2Al(H)(μ2-H)2Ti[η5-C5(CH3)5]2

Interaction between (η⁵-C₅Me₅)₂TiH₂BH₂ LiAlH₄ in ether produced the complex [(η⁵-C₅Me₅)₂TiH₂AlH₂]₂. The compound crystallized in a monoclinic unit cell with the parameters a 11.196(4), b 8.915(3), c 20.777(7) Å, γ 101.74(3)°, space group P2₁/n, Z = 4. The linkage between the Ti and Al atoms is accomplished via the double hydrogen bridge TiH₂Al, whereas dimerization occurs via the AlH₂Al bridges. The coordination polyhedron for the Al atom is a distorted trigonal-bipyramid with five hydride ligands at its apices. Decomposition of [(η⁵-C₅Me₅)₂TiH₂AlH₂]₂ in solution produced the complex [(η⁵-C₅Me₅)₂Ti]₂AlH₅, crystallizing in a triclinic unit cell with the parameters a 11.881(4), b 18.951(8), c 8.868(3) Å, α 93.04(3), β 104.33(3), γ 79.26(3)°, space group P$\text{1}$, Z = 2. The Al atom in this compound is assumed to have coordination number 5 and to be surrounded by hydride hydrogens only. The isomerization rate for 1-hexene in the presence of [(η⁵-C₅Me₅)₂TiH₂AlH₂]₂ was 0.3 mol olef/g-atom Ti·min, while the hydrogenation rate of the complex [(η⁵-C₅Me₅)₂Ti]₂AlH₄Cl was 38 mol H₂/g-atom Ti·min.     

Effect of the growth rate on thermal conditions during the growth of single crystals with melt feeding

An attempt is made to establish a correlation between the radial and axial growth rates and the change in the conditions of heat transfer from a growing crystal to the atmosphere of the water-cooled vacuum furnace for the growth of large alkali halide single crystals. It is found experimentally that an increase in the growth rate leads to an increase in the automatic compensation of the melt temperature by the main heater. In this case, the thickness of the layer of melt condensate on the end face and the lateral surface of the crystal decreases. It is revealed that the possibility of growing infinitely long ingots in the presence of intense melt evaporation is restricted by the possibilities of the heat transport through the boundary between the furnace atmosphere and the cooled furnace walls, onto which melt condensate deposits.     

Chemistry of Ruthenium Polypyridine Complexes: IV. Quantum-Chemical Simulation of the Effect of Solvation Shell on the Electronic Structure of Ru(II) Complexes with Nitrogen-containing Ligands

Ab initio quantum-chemical calculations of Ru(II) complexes have been fulfilled with consideration for solvation within the framework of the polarized continuum model. Energy levels of fragments of Ru(II) complexes with organic ligands are shifted relative to each other by electrostatic interactions with the solvation shells.     

Ambient temperature or moderately cooled semiconductor hot electron bolometer for mm and sub-mm regions

A model of semiconductor hot electron bolometer (SHEB), in which electromagnetic radiation heats only electrons in narrow-gap semiconductor without its lattice slow-response heating, is considered. Free carrier heating changes the generation-recombination processes that are the reason of semiconductor resistance rise. It is estimated, that Hg_0.8Cd_0.2Te detector noise equivalent power (NEP) for mm and sub-mm radiation wavelength range can reach NEP ∼10⁻¹¹ W at Δf = 1 Hz signal gain frequency bandwidth. Measurements performed at electromagnetic wave frequencies v = 36, 39, 55, 75 GHz, and at 0.89 and 1.58 THz too, with non-optimized Hg_0.8Cd_0.2Te antenna-coupled bolometer prototype confirmed the basic concept of SHEB. The experimental sensitivity S_v ∼2 V/W at T = 300 K and the calculated both Johnson-Nyquist and generation-recombination noise values gave estimation of SHEB NEP ∼3.5 × 10⁻¹⁰ W at the band-width Δf = 1 Hz and v = 36 GHz.