[en] A crystal of K₂M/sub x/Zn/sub 1-x/(dp)₂ x nH₂O, where M = Cu(II) or Mn(II), has been investigated by ESR at 9 and 36 GHz in the 4.2-300⁰K temperature range. The ESR spectra of the Cu(II) ions have a symmetry no higher than orthorhombic in the entire temperature range investigated. A temperature dependence of the spectra of the Cu(II) ions, which is absent in the spectra of the Mn(II) ions and can be explained in the framework of the pseudo-Jahn-Teller effect, has been discovered. The influence of the second coordination sphere of the Cu(II) ion on the direction of the axes of the g and A tensors has been discovered

[en] The crystal and molecular structures of the trinuclear molecular cluster Fe₃(μ₃-O)(CF₃COO)₆](C₆H₅)₃PO]₃ have been determined: α = 22.045(10), b = 26.390(11), c = 14.265(9) A, γ = 61.90(2)⁰, Z = 4, space group P2₁/b (diffractometer, λCu Kα, 2939 reflections, R = 0.074). The iron atoms are located at the corners of an almost equilateral triangle with sides measuring 3.325-3.374 A. The central bridging O(4) oxygen atom joins all three iron atoms, which are joined further in pairs by six bridging CF₃COO groups acting as bidentate ligands. The coordination of each iron atom is completed to octahedral by the triphenylphosphine oxide ligands. Gamma-resonance spectroscopy in the 80-300⁰K temperature range has revealed a change in the character of the spectra at a temperature >210⁰K, which is interpreted as the temperature for delocalization of an electron over a system of three centers corresponding to a gamma-resonance time scale of ∼ 10^-7 sec. At 300⁰K the gamma-resonance spectra describe three different states for the iron atoms, in agreement with the x-ray data

[en] The reactions of 5-aminouracil and its derivatives with cis-[Pt(NH₃)₂Cl₂] in neutral and alkaline media have been investigated. It has been established by the methods of elemental analysis, electrical conductivity measurements, and UV, IR, and PMR spectroscopy that 5-aminouracil, unlike uracil and its derivatives with electronegative substituents (F, Cl, Br, NO₂) in position 5, forms a covalent bond with Pt(II) at its C(6) carbon atom with simultaneous coordination of the nitrogen atom of the exocyclic amino group to a second platinum atom in a neutral medium. 5-Amino-6-methyluracil forms a complex compound of the chelate type with Pt(II) with the participation of the O(4) oxygen and the exocyclic amino group in the coordination. 5-Diethylaminouracil does not undergo a complexation reaction with Pt(II) in a neutral medium. Coordination of the anion of the ligand at N(3) of the heterocycle occurs in an alkaline medium, as was previously observed for other 5-substituted uracils

[en] The crystal structure of the compound Eu(DBM)₂NO₃(TPPO)₂ has been determined (DAR UMB-K instrument, MO Kα, spherical sample, heavy-atom method, least-square method in the anisotropic approximation on the basis of 2090 reflections to R = 0.106). The crystals are monoclinic: a = 28.029(4), b = 20.698(3), c = 12.964(3) A, γ = 127.87(1)⁰, d/sup (mea)/ = 1.37, d/sup (cal)/ = 1.36 g/cm³, μ(Mo Kα) = 11.6 cm^-1, Z = 4, space group B2/b. In the isolated molecular complex Eu(DMB)₂NO₂(TPPO)₂ the europium atom is located on a twofold rotational symmetry axis. The coordination polyhedron of Eu is a distorted dodecahedron. The lengths of the Eu-O(DBM), Eu-O(TPPO), and Eu-O(NO₃) bonds are equal to 2.247(9)-2.335(2), 2.312(5), and 2.549(3) A, respectively. The Eu-NO₃ chelate ring is planar. The coordination of the phosphorus atom is tetrahedral. The Eu(DMB) fragment of the complex has a slight fold along the O(1)...O(2) line (the angle equals 6.9⁰). The packing of the molecules in a crystal is governed only by van der Waals interactions. It has been postulated that in adducts of europium with neutral ligands the splitting of the Stark components of Eu(III) decreases with decreasing values of the width of the coordination layer ΔR

[en] The question of the structure of complexes of the type trans-Cu/sup II/ (NH₃)₂Hal₄ has been studied from the point of view of the theory of the Jahn-Teller effect. It has been shown that the existence of two isomers with D/sub 4h/ and D/sub 2h/ symmetry in such complexes can be explained when the linear and quadratic terms in the vibronic coupling operator and the differences between the ligands in the first coordination sphere of the metal are taken into account without relying on any intermolecular interactions. An explanation for the experimentally observed interatomic distances in the chainlike compounds with Hal = Br and Cl requires consideration of the interaction of the Jahn-Teller e/sub g/* orbitals with the higher lying α/sub 1g/* state

[en] A method for the synthesis of coordination compounds of metals containing deprotonated residues of the imidothiol tautomeric form of thiosemicarbazide has been developed. It has been shown that complexes of this type can be obtained in two ways: (1) by carrying out reactions between thiosemicarbazide and metal salts in a weakly alkaline medium; (2) by alkalinizing aqueous solutions containing complexes with neutral thiosemicarbazide molecules. The cobalt complex Co(L - H)₃ and the nickel complex Ni(L - H)₂, as well as the previously known compounds of zinc and cadmium with the formulas Zn(L - H)OH·H₂O and Cd(L - H)₂, where L stands for molecule of thiosemicarbazide, have been obtained on the basis of the synthesis method developed. The properties of all of the complexes synthesized have been characterized

[en] Parametrization of the CNDO method for Mo, Tc, And Re has been presented. The parameters were determined as a result of a comparison of the electronic structure of [M₂Cl₈]/sup n-/ (M = Mo, Tc, Re; n = 4, 3, 2) obtained by the CNDO method with the results of calculations by the SCF-X/sub α/-SW method, as well as an ab initio method. The results obtained with the use of parameters determined by such a method permit the correct description of the distribution of the charges in complexes, bond orders, and orbital energies, but they do not provide a satisfactory description of electronic transitions

[en] The reactions of [Rh(CO)₂Cl]₂ (Y₀) with cyclooctene and several other olefins (1-heptene, 1-hexene, ethylene, and cyclohexene) have been studied by IR and ¹³C NMR spectroscopy. The main reaction products are the binuclear complexes Rh₂L(CO)₃Cl₂ (Y₁) and [RhL(CO)Cl]₂ (Y₂), where L denotes the olefin. The extent of replacement of the carbonyl groups depends on the nature of the olefin and the conditions under which the reaction is carried out (the L:Rh ratio and the removal of CO from the reaction sphere). The liquid olefins form the following series according to their ability to replace the carbonyl groups: C₈H₁₄ > C₇H₁₄, C₆H₁₂ > C₆H₁₀. In the presence of an excess of C₈H₁₄, Y₂ disproportionates with the formation of a dicarbonyl product, which presumably corresponds to the formula Rh(C₈H₁₄)₂(CO)₂Cl (a pentacoordinate complex with a trigonal-bipyramidal structure). The ¹³C signal in the NMR spectrum of a solution of Y₂ in C₈H₁₄ is a singlet with σ(¹³C) 180.3 ppm, which is an indication of the rapid exchange of the carbonyl groups. Rapid exchange of the CO ligands is also observed in solutions of Y₀ in the olefins (with the exception of C₆H₁₀). For example, the ¹³C signal in the spectrum of a solution of Y₀ in C₈H₁₄ is a singlet with σ(¹³C) 179.8 ppm. The spectrum of Y₀ in C₆H₁₀ is a doublet with σ(¹³C) = 178.5 ppm and ¹J(CRh) = 76.3 Hz. A scheme for the interaction of Y₀ with olefins based on the conception of the trans antagonism of π-acceptor ligands has been proposed

[en] The absolute signs of the components of the A and A/sup L/ tensors and their mean values have been analyzed on the basis of models of the structure of the delocalized metal-ligand bonds in square-planar complexes of Cu²⁺ with heavy ligands (Cl, Br), on which information can be obtained from the solution of the inverse problem of ESR spectroscopy, i.e., the calculation of the coefficients in the expansions of MO's in orbitals of the atoms appearing in the complexes from experimental values of the components of the g, A, and A/sup L/ tensors and the energy gaps for the d-d transitions. It has been established that the components of the A and A/sup L/ tensors have opposite signs: A/sub parallel/ < 0, A/sub perpendicular to/ < 0, A/sub parallel//sup L/ > 0, A/sub perpendicular to//sup L/ > 0. It has been shown that consideration of the second-order contributions of the components of the A/sup L/ tensor does not result in changes in the signs, although it is necessary for the correct description of metal-ligand chemical bonds in tetragonal complexes of Cu²⁺

[en] Investigations of the absorption spectra of solutions of the complex compounds of chromium(III) with dimethylformamide, dimethyl sulfoxide, urea, and ethylenediamine have been carried out. The influence of the temperature and the nature of the ligands on the separation of the spin-forbidden ²E/sub g/ withdraws ⁴A/sub 2g/ and ²T/sub 1g/ withdraws ⁴A/sub 2g/ transitions and the spin-allowed ⁴T/sub 2g/ withdraws ⁴A/sub 2g/ transitions in the absorption spectra of solutions of the complex compounds of Cr(III) with O/sub h/ symmetry has been determined. The dependence of the value of the parameter Dq on the temperature has been confirmed. The presence of a vibronic structure for both energetically lower intersystem-crossing transitions in the absorption spectra of [Cr(DMF)₆](ClO₄)₃ in frozen dimethylformamide (T = 77⁰K) has been discovered