Voltammetric studies of the Kolbe synthesis with perfluorocarboxylic acids prepared from hexafluoropropene oxide oligomers

Carboxylic acids prepared from hexafluoropropene oxide CF₃CF₂CF₂O[CF(CF₃)CF₂O]_nCF (CF₃)COOH [n = 0, 2,5-bis(trifluoromethyl)-3,6-dioxaperfluorononanoic acid; n = 1, 2,5,8- tris(trifluoromethyl)-3,6,9-trioxaperfluorododecanoic acid], according to voltammetric data, enter the Kolbe reaction both at the Pt anode and at anodes from carbon materials in H₂O-CH₃CN and CH₃OH-CH₃CN solutions. The critical potential appreciably depends both on the anode material and on the solvent composition. Favorable effect of pyridine additions in H₂O-CH₃CN solutions is due to replacement of water molecules from the electrical double layer. The sodium ions exert a negative effect on the Kolbe synthesis.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1842–1846.Original Russian Text Copyright © 2004 by Chechina, Sokolov, Tomilov.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis and crystal structure of Nb2S4(S2NCEt2)4, the first molecular complex containing an [Nb2(μ2-S2)2]4+ fragment

The crystal structure was determined for Nb₂S₄(S₂NCEt₂)₄ obtained in 48% yield by the reaction of Cs₄Nb₂S₄(NCS)₈ with NaS₂CNEt₂ in water: a=21.181(8), b=6.958(1), c=16.623(6) Å, =133.95(2)^o, V = 1764(1) ų, space group C2/m, Z=2, d_calc=1.708 g/cm³. The measurements were carried out on a Syntex P2₁ diffractometer with CuK radiation. A total of 2536 reflections were measured, of which 990 were used, R_aniso=0.0444. The basic fragment in this molecule is [Nb₂(₂–S₂)₂]⁴⁺, the Nb–Nb distance in which corresponds to a metal-metal single bond. The molecule is partially disordered over two positions about the twofold axis and mirror plane of the C2/m space group. The dithiocarbamate and disulfide ligands with bidentate coordination form a distorted square antiprism about each of the niobium atoms as in NbS₂Cl₂. The anomalously large S–S bond length in the S₂ ligand [2.282(5) Å] may be attributed to inaccuracy in the determination due to disorder.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 2, pp. 134–138, March–April, 1993.     

Fullerenes as a new type of ligands for transition metals

Fullerenes are considered as ligands in transition metal π-complexes. The following aspects are discussed: metals able to form complexes with fullerenes; haptic numbers; homo-and heteroligand complexes; ligand compatibility with fullerenes for different metals, including fullerenes with a disturbed structure of conjugation.     

The problem of fullerenes. The chemical aspect

The preparation, structure, and reactivity of the family of polyhedral carbon clusters, novel allotropes of carbon, are reviewed.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 10–19, January, 1993.     

Fluorinated triazinones from hexafluoroacetone ethoxycarbonylimine

The behavior of hexafluoroacetone ethoxycarbonylimine in cyclocondensation with different binucleophiles of the amidine type, viz., amino derivatives of N- and N,S-heterocycles, was studied. A preparative method for the synthesis of previously unknown annelated 2,2-bis(trifluoromethyl)-1,3,5-triazinones was developed.     

Design of scaffold-like metal-organic coordination polymers based on dinuclear zinc(<Emphasis Type="SmallCaps">II</Emphasis>) carboxylate complexes

Two new scaffold-like metal-organic coordination polymers, [Zn₂ndc₂bpe]·DMF and [Zn₂ndc₂dedpbp] ·4DMF (ndc is 2,6-naphthalenedicarboxylate, bpe is trans-bis(4-pyridyl)ethylene, and dedpbp is 4,4′-diethynyl-4″,4′″-dipyridylbiphenyl), were synthesized by heating stoichiometric amounts of zinc(II) nitrate, H₂ndc, and bpe or dedpbp in DMF. The structures of the polymers were established by X-ray diffraction. Coordination of linear dicarboxylate ligands to zinc cations gives rise to planar square-grid networks, and additional coordination of the bifunctional nitrogen-containing ligands results in the formation of scaffold-like triply interpenetrating structures with a primitive cubic topology. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 219–223, February, 2007.     

Influence of pore diffusion on the rate of n-heptane conversion on a Pt/Al2O3 catalyst under reforming conditions

Under reforming conditions, the rate of n-heptane conversion on a large Pt/Al₂O₃ catalyst grain, in contrast to that in the kinetic region, depends on the hydrogen to hydrocarbon mole ratio. The rate equation for the reaction on a large grain agrees well with the experimental results obtained by a gradientless method under pressure.

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