Structure of chlorotris(1,3,5-triaza-7-phosphaadamantane)platinum(II) chloride hydrate methanolate, [Pt(PTA)3Cl] [Cl]·H2O·CH3OH

The title compound chlorotris(PTA)platinum(II) chloride hydrate methanolate (PTA=1,3,5-triaza-7-phosphaadamantane), [C₁₉H₄₂Cl₂N₉O₂P₃Pt] is monoclinic, witha=10.832(1),b=21.306(7),c=12.702(3)Å,=100.42(5)°,V=2883(2)ų,Z=4,D _x=1.814 g cm^–3,=53.0 cm^–1,F(000)=1568,T=298K in space groupP2₁/c. The structure was solved by heavy atom and Fourier methods and refined toR=0.051 for 4319 unique observed reflections. The complex exhibits approximately square-planar geometry about the Pt atom and a significant trans effect, with bond lengths Pt-Cl1=2.3371(2), Pt-C12 (ionic)=4.463(4), Pt-P _{trans(to cl)}=2.233(2), Pt-P _cis,ave=2.323(3)Å and bond angles Cl-Pt-P _cisave 83.60(3), P _trans -Pt-P _cis,ave 96.49(6)°. The H₂O is apparently hydrogen bonded to two N atoms on different cations, and the methanol OH group to the chloride anion.     

The low-temperature specific heat of PTFE (Teflon) at pressures to 5.2 kbar

The specific heat of PTFE (Teflon) has been measured between 0.3 and 20 K at zero pressure, and between 1 and 20 K at five other pressures ranging up to 5.2 kbar. The specific heat anomalies typical of amorphous materials were observed. The linear term is smaller than for other organic polymers and is closer in magnitude to those of high purity glassy insulators. At zero pressure the T³ term in the specific heat exceeds that calculated from the sound velocities by 24%. The evolution with pressure of the T³ term and of the maximum in C/T³ are very similar, suggesting a close relation between the vibrational modes that contribute to these features in the specific heat. This result and the relatively simple structure of Teflon rule out independent localized oscillators as the source of the maximum in C/T³.     

Novel Mixed Complexes of Copper(II) and Ethylenediamine: Synthesis,Crystal Structure,and Catalytic Activity in the Cross-Coupling Reaction of 1-Phenyl-5<Emphasis Type="Italic">H</Emphasis>-tetrazole-5-thiol and Iodobenzene

Two earlier unknown complexes, [Cu(en)₂(Hptt)]Br (Hptt = 1-phenyl-1H-terazole-5-thiol, en = ethylenediamine) and trans-[Cu(en)2(H2O)Br]Br, have been synthesized and characterized using X-ray diffraction analysis. In [Cu(en)₂(Hptt)]Br complex, the copper cation is bonded with the N⁴ atom of tetrazole ring. Catalytic activity of the obtained complexes in cross-coupling reaction of 1-phenyl-5H-tetrazole-5-thiol with iodobenzene is comparable to that of CuBr₂ in the presence of 2 eq. of ethylenediamine.     

A superconducting direct-current limiter with a power of up to 8 MVA

A resistive switching superconducting fault current limiter (SFCL) for DC networks with a nominal voltage of 3.5 kV and a nominal current of 2 kA was developed, produced, and tested. The SFCL has two main units—an assembly of superconducting modules and a high-speed vacuum circuit breaker. The assembly of superconducting modules consists of nine (3 × 3) parallel–series connected modules. Each module contains four parallel-connected 2G high-temperature superconducting (HTS) tapes. The results of SFCL tests in the short-circuit emulation mode with a maximum current rise rate of 1300 A/ms are presented. The SFCL is capable of limiting the current at a level of 7 kA and break it 8 ms after the current-limiting mode begins. The average temperature of HTS tapes during the current-limiting mode increases to 210 K. After the current is interrupted, the superconductivity recovery time does not exceed 1 s.     

Catalytic asymmetric generation of (Z)-disubstituted allylic alcohols

A one-pot method for the direct preparation of enantioenriched (Z)-disubstituted allylic alcohols is introduced. Hydroboration of 1-halo-1-alkynes with dicyclohexylborane, reaction with t-BuLi, and transmetalation with dialkylzinc reagents generate (Z)-disubstituted vinylzinc intermediates. In situ reaction of these reagents with aldehydes in the presence of a catalyst derived from (-)-MIB generates (Z)-disubstituted allylic alcohols. It was found that the resulting allylic alcohols were racemic, most likely due to a rapid addition reaction promoted by LiX (X = Br and Cl). To suppress the LiX-promoted reaction, a series of inhibitors were screened. It was found that 20-30 mol % tetraethylethylenediamine inhibited LiCl without inhibiting the chiral zinc-based Lewis acid. In this fashion, (Z)-disubstituted allylic alcohols were obtained with up to 98% ee. The asymmetric (Z)-vinylation could be coupled with tandem diastereoselective epoxidation reactions to provide epoxy alcohols and allylic epoxy alcohols with up to three contiguous stereogenic centers, enabling the rapid construction of complex building blocks with high levels of enantio- and diastereoselectivity.     

Spiral coils for counter-current chromatography using aqueous polymer two-phase systems

Retention properties of polyethylene glycol-phosphate aqueous two-phase systems in a spiral coil (5 mm I.D.) on Type-J synchronous counter-current chromatographic devices have been compared for the elution mode where the lower phase is the mobile phase and flows from the inside head terminal. This was achieved with the aid of digital imaging under stroboscopic illumination, an image analysis and measurement of the displaced volume of the stationary phase. For the spiral coil, high and stable stationary phase retention at mobile phase flow rates up to 64 ml/min has been obtained. Wave-like disturbance of the interface near the proximal point was observed and analyses have been made for possible use in protein separation.     

Phase separation in La-Pr manganites and its evolution in a magnetic field

The self-consistent harmonic oscillator model including the three-dimensional cranking term is extended to describe collective excitations in the random phase approximation. It is found that quadrupole collective excitations associated with wobbling motion in rotating nuclei lead to the appearance of two-or three-dimensional rotation.     

Dosage d'oxydes de tantale,niobium et titane dans leurs mélanges par radioactivité

The oxides of niobium, tantalium and titanium can be determined in their mixtures by means, of radioactive tracers. Two methods have been studied.1st method. On irradiation of the mixture with slow neutrons and measuring the activity of the ¹⁸²Ta formed, tantalium can be determined within about 10% in mixtures poor in this element.2nd method. It is an improvement of the classical method of separation of these oxides by tannin. ⁹⁵Nb of known specific activity is added to the solution, to be determined, then tantalium, together with a part of the niobium, is precipitated by tannin at ph 3.8. Niobium is then precipitated in the filtrate at a higher pH. The activity measurement of the two fractions allows the determination of how the partition is effected and the introduction of the necessary correction. Titanium is determined by colorimctry after calcination of the redissolvcd oxides.     

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