The mutual influence of ligands in transition metal bis-chelates

Electronic structure quantum chemical calculations of the Fe(II), Ni(II) and Cu(II) bis-chelate series are reported. The nature of the ligand mutual influence effect on these compounds is elucidated. This effect manifests itself in polarization of metal—ligand bonds. The ligands which have highly covalent bonds with the metal form bonds of even greater covalent character in mixed complexes, whereas bonds for the other ligands become more ionic.     

Electronic regioselectivity in the reactions of pyridinium ylides with tetracyanoethylene

Highly regioselective reactions of pyridinium ylides with tetracyanoethylene occur via an Ad_N-E mechanism to form Z-isomers of 3-aroyl-3-(1-pyridinio)-1,1,2-tricyano-2-propenides-1, corresponding in structure to 1,4-ylides with maximum charge separation. If the unsaturated nitrite starting material contains a nucleofugal group 1,2-elimination predominates over 1,3-elimination.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1087–1094, August, 1991.     

Molecular structure of N-mesityl-6H-anthra[9,1-bc]pyrrol-6-one

The molecular and crystalline structure of 1-(2,4,6-trimethylphenyl)-6H-anthra-[9,1-bc]pyrrol-6-one was determined by the x-ray structural method. There is a larger uniformity of the bonds in the benzene ring of the isoindole fragment than in the N-substituted isoindoles; this derives from the electronic influence of the keto group. The structure of the whole molecule does not have marked 1,10-anthraquinoid character.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 485–490, April, 1988.     

Photoinduced structure transformations in dichromate-impregnated denatured collagen

X-ray structure analysis shows that irradiating gelatin films containing chromates causes a spiral-coil transition in the denatured collagen molecules. The concentration and type of the chromate have substantial effects, as do the film preparation conditions. The x-ray diffraction and ESR data indicate that chromium(V) compounds formed by photoreduction from chromium(VI) ones are mainly responsible for the conformation transition. In the absence of chromium compounds, light absorbed by the gelatin macromolecules results in macroradicals on account of the photolysis in the denatured protein chains. There is no phase transition.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No, 2, pp. 247–251, March–April 1988.     

Condensation of aryl bromides with styrenes,catalyzed by nickel complexes in the presence of zinc

Conclusions Condensation of aryl bromides with styrenes in acetonitrile in the presence of nickel organometallic complex catalysts and metallic zinc occurs regio- and stereoselectively to give E-stilbenes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2508–2511, November, 1987.