A FLATTENED OCTAHEDRON – THE METAL ENVIRONMENT IN COMPLEXES WITH PYRROLYL-SUBSTITUTED NITROXIDE DIRADICALS

Journal of Structural Chemistry - The structures of Ni(II), Cu(II), and Zn(II) complexes with anions of 2,5-pyrrolyl-disubstituted nitronyl nitroxide (L1) and iminonitroxide (L2) diradicals (HL1 is...     

Effect of increasing pressure on the structure and temperature-induced changes in magnetic properties of heterospin complexes

Russian Chemical Bulletin - The study is concerned with structural rearrangements in the crystals of heterospin complexes Cu(hfac)2 with nitroxide radicals LR (hfac is hexafluoroacetylacetonate, LR...     

Biferrocenes and terferrocenes

Russian Chemical Bulletin -     

Two Isomers of C6H6F9O9Tb

Two isomers with empirical formula C₆H₆F₉O₉Tb are synthesized and their structures are studied. Isomerism was found to arise due to different positions of a proton. Crystals of two isomers are isostructural and form continuous series of solid solutions with C₆H₆F₉O₉Eu.     

Effect of Oxygen Redistribution on the Normal and Superconducting Properties of Yttrium High‐Temperature Superconductors

An anomaly is found in the vicinity of T_max 560$ K on electric resistance versus temperature curves for yttrium hightemperature superconductors of the 123 phase. Xray phase analysis suggests a structural phase transition in the vicinity of T_max due to oxygen redistribution in the mobile sublattice of this compound. Investigation of samples with Y partially replaced by Ca has shown that the structural phase transition does not depend on carrier concentration in the conduction band.     

Sigma complexes in the pyrimidine series. 2. σ Complexes of 5-nitropyrimidine and methoxy-substituted 5-nitropyrimidines with the acetone anion

The corresponding σ complexes of the Meisenheimer type, viz., anions of the potassium salts of 6H-5-nitro-6-acetonylpyrimidines, were obtained and isolated in the reaction of 5-nitro-, 5-nitro-4-methoxy-, 5-nitro-2-methoxy-, and 5-nitro-2,4-dimethoxypyrimidines with acetone in the presence of potassium hydroxide. The structures of the complexes were proved by means of the PMR, IR, and UV spectra. It is shown that the acetone anion in all cases adds to the methoxy-unsubstituted position of the pyrimidine ring, whereas nucleophilic attack takes place at the C₄ atom when the 2 and 4 positions are free. See [1] for communication 1. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 239–242, February, 1980.     

Crystal structure of the Ni(II) complex with the nitroxyl radical derivative of 3-imidazoline and 1-butanol

The crystal structure was found for the Ni(II) complex with the nitroxyl radical derivative of 3-imidazoline L=C₁₀H₁₃N₂O₂F₃ and 1-butanol C₄H₉OH with the formula NiL₂(n-C₄H₉OH)₂ (a=10.907(2), b=16.769(5), c=12.321(3) Å, =96.33(2), =120.36(1), =106.3(2)^o, V = 1780.7(7) ų, d_calc=1.32 g/cm³, space group P1, Z=2, R=0.072). The structure was molecular in nature. Octahedral coordination of the nickel ion was found with the oxygen and nitrogen atoms of two bidentate L in the equatorial plane [Ni–O, 2.13 Å (av.); Ni–N, 1.99 Å (av.)] and the oxygen atoms [Ni–O_OH, 2.13 Å (av.)] of the OH groups of the alcohol molecules in the axial positions. The rather strong hydrogen bonds between the coordinated OH groups of the alcohol and oxygen atoms of the groups of the adjacent complex molecules (O...O, 2.78–2.84 Å) delineate layers, in which the distances between the paramagnetic sites of adjacent molecules Ni... are shorter than the intramolecular distances and much shorter than the analogous distances between adjacent layers. On the whole, this structure is similar to those of analogous compexes with other alcohols previously studied.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 2, pp. 119–125, March–April, 1993.     

Properties and structures of porphyrexides

The molecular and crystal structures of porphyrexides, viz., 4-amino-2-imino-(1) and (Z)-2-amino-4-bromoimino-5,5-dimethyl-4,5-dihydro-1H-imidazole 1-oxyls (7), and their diamagnetic precursors were determined. Compound 1 is kinetically unstable because it is oxidized with atmospheric oxygen to form (E)-1,2-bis[1-amino-1-(cyanoimino)-2-methyl-propan-2-yl]diazene 1,2-dioxide. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 441–447, March, 2006.     

Molecular magnet based on the FeII,III complex with squaric acid

The reaction of Fe^II and Fe^III salts with tetrabutylammonium squarate in an aqueous solution gives rise to a new molecular magnet (T _c = 8.6 K).