The signature of the Ricci curvature of left-invariant Riemannian metrics on four-dimensional Lie groups. The nonunimodular case

We obtain a complete classification of all the possible values of the signature of the Ricci curvature of left-invariant Riemannian metrics on four-dimensional nonunimodular Lie groups.     

The solid complex Zn(CF3)Br·2DMF as an alternative reagent for the preparation of both, trifluoromethyl and pentafluoroethyl copper, CuCF3 and CuC2F5

Trifluoromethylcopper and pentafluoroethylcopper are prepared conveniently via the reaction of the solid complex Zn(CF₃)Br·2DMF with copper(I) bromide in N,N-dimethylformamide. The reactions of both copper species with 2,4-dinitrochlorobenzene, 4-iodonitrobenzene, 4-nitrobenzyl iodide, 4-bromobenzoic acid ethyl ester, 4-iodobenzoic acid ethyl ester, 2-iodopyridine and 2-iodopyrimidine have been studied. The structure of 2,4-dinitrotrifluoromethylbenzene has been elucidated.     

Fluoride-mediated selective cross-coupling reactions of alkyl halides and trimethyl(perfluoroalkyl)silanes, Me3SiRf (Rf = CF3, C2F5) in the absence of any catalysts

A temperature range of −18 °C to room temperature was found to be effective for selective fluoride-mediated cross-coupling reactions of trimethyl(perfluoroalkyl)silanes, Me₃SiCF₃ and Me₃SiC₂F₅, and alkyl halides, RX (X = Br, I) in the absence of any catalyst.     

Chlorination of 4-methyl-8-methoxy-2,3-dihydro-1H,1,5-benzodiazepin-2-one

The results of the chlorination of 4-methyl-8-methoxy-2,3-dihydro-1H,1,5-benzodiazepin-2-ones are compared with the results of quantum-chemical calculations of 4-methyl-2,3-dihydro-1H-1,5-benzodiazepin-2-ones with various substituents in the benzene ring in the case of homolytic halogenation. The chlorination of 4-methyl-8-methoxy-2,3-dihydro-1H-1,5-benzodiazepin-2-one (I) with N-chlorosuccinimide leads to 3-chloro- and 3,3-dichloro-4-methyl-8-methoxy-2,3-dihydro-1H-1,5-benzodiazepin-2-ones, whereas chlorination with sulfuryl chloride leads to 4-chloromethyl and 3,3-dichloro-4-methyl derivatives. The IR, PMR, and mass spectra of the synthesized compounds are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1272–1274, September, 1981.     

Phenols Reactions with 1,1-Difluorodichloroethene, 1,2-Di(fluorochloro)ethene,and Trifluorochloroethene

Phenols containing in the para-position of the benzene ring substituents of various electronic character add to 1,1-difluorodichloroethene in acetone in the presence of potassium hydroxide. A similar reaction with 1,2-di(fluorochloro)ethene occurs only in DMF or N,N-dimethylacetamide and is followed by hydrogen chloride elimination. Phenols with electron-donor substituents add to trifluorochloroethene in acetone in the presence of potassium hydroxide, the reaction of phenols with electron-acceptor substituents requires DMF as solvent.     

Transition Metal Ion-binding Properties of a 14-Membered N2O2S2- Macrobicyclic Ligand

The selective liquid–liquid extraction of various transition metal cations from the aqueous phase to the organic phase was carried out using a 14-membered N₂O₂S₂-macrobicycle. Metal picrates such as Pb²⁺, Co²⁺, Zn²⁺, Ni²⁺,Cu²⁺ and Cd²⁺ were used in this extraction studies. It was found that the ligand showed moderate selectivity towards Pb²⁺ only among the other metals. The extraction constant (log K _ex) was determined to be 13.8 for Pb²⁺ complex.     

Nuclear spin-lattice and nuclear spin-spin relaxation time measurements in EuB6 at low temperatures using the spin-echo technique

Experimental results on the nuclear spin-lattice and nuclear spin-spin relaxation times in the ferromagnetic EuB₆ at temperatures below 4·2 K are presented using the external magnetic field,H _ext, in the range of 0 ⩽H _ext ⩽ 10 kG. Nuclear spin-spin relaxation time computed on the basis of the Suhl-Nakamura process turns out to be 3·2μs, which compares well with the experimental value 11·1μs obtained with the 10 kG magnetic field at 1·7 K. It is found that in the ferromagnetic EuB₆,T ₁ is approximately 5 × 10³ times larger thanT ₂ at 1·7 K with the 10 kG magnetic field. Thus the effect ofT ₁ onT ₂ can be neglected. From the experimental value ofT ₂, the value of the homogeneous line broadening is found to be 14 kHz. The corresponding value obtained from the cw method is 175 kHz. This evidently shows the presence of the inhomogeneous line broadening in the cw NMR.