Russian Journal of Coordination Chemistry

The synthesis, characterization, and molecular structural properties of a Schiff base complex with 2,6-diacetyl pyridine are reported. The quantum chemical study with combined X-ray data for a tridentate Schiff base ligands are presented. All calculations were performed by using ab initio calculations as implement in the Gaussian-03 program package, and full geometry optimization was used in the gas phase. The Mulliken population study shows three nitrogen atoms in this structure in the coordination sites for binding to the metal ions.

Single crystals of [(C5H4NH)NC4H8NH(C3H5)]2+[Cu3Cl5]2− are obtained by ac synthesis in ethanol from 1-(2-pyridyl)-4-allyl-piperazinium and Cu(II) dichlorides and their structure is studied by X-ray diffraction analysis (space group P-1, a = 7.246(7) Å, b = 8.54(1) Å, c = 16.41(1) Å, α = 70.76(8)°, β = 77.24(8)°, λ = 80.42(9)°, V = 30(4) Å3, Z = 2, R(F) = 0.0686. In the structure of this π-complex, the Cu and Cl atoms form unusual centrosymmetrical Cu6Cl10 fragments, each fragment being bonded to two 1-(2-pyridyl)-4-allyl-piper-azinium cations via π-interaction Cu-(C=C). A three-dimensional structure is formed by means of N-H…Cl hydrogen bonds. The trigonal-pyramidal surrounding of the Cu(1) atom includes three Cl atoms and the C=C bond, while the tetrahedral surrounding of Cu(2) and the trigonal surrounding of Cu(3) involve the Cl atoms only.

μ-Oxo-bis[(bromo)tri-m-tolylantimony] was synthesized by the reaction of tri-m-tolylstibine with hydrobromic acid in ether in the presence of hydrogen peroxide. The complex was structurally characterized by X-ray diffraction analysis. The coordination polyhedron of the Sb atoms is a distorted trigonal bipyramid with the bromine and the bridging O atoms in the axial positions. The Sb(1)–C(Ph) distances vary from 2.085(9) to 2.111(8) Å. The Sb(1)–Br(1) and Sb(2)–Br(2) bond lengths are 2.739(2) and 2.735(2) Å, respectively; the Sb–Obr distances measure 1.949(1) Å.

The spectral characterization of cadmium(II) complexes of the general formula [Cd(Tmtu)2X2] (Tmtu = tetramethylthiourea, X = Cl−, Br−, I−, and SCN−) as well as the X-ray structure of one of them, [Cd(Tmtu)2Cl2] (I) is described. In (I), the cadmium atom lies on a twofold rotation axis and has a distorted tetrahedral coordination environment defined by two S atoms of telramelhylthioures (Tmtu) ligands and two chloride ions. The crystal structure is stabilized by non-classical intramolecular C-H⋯N and C-H⋯S hydrogen bonding interactions involving the methyl H and sulfur or nitrogen atoms. The spectroscopic data were discussed in terms of the nature of bonding.

An Erratum to this paper has been published: https://doi.org/10.1134/S1070328422340012

A new zinc(II) coordination polymer, {[Zn(HCAM)(4,4′-Bipy)0.5] · H2O} n (I) (H3CAM = 4-hydroxypyridine-2,6-dicarboxylic acid; 4,4′-Bipy = 4,4′-bipyridine), has been synthesized by hydrothermal reaction of Zn(OAc)2, H3CAM and 4,4′-Bipy. It has been structurally characterized by element analysis, IR-spectra. X-ray single-crystal analysis was carried out for I (CIF file CCDC no. 974199), which crystallizes in the orthorhombic system, space group Pbca. The single X-ray diffraction studies reveal that I shows a new 2D wave-like plane with 3-connected net. Furthermore, the thermal stability of compound I was studied.

Chemical equilibria in aqueous solutions of chromium sulfate are studied and the mathematical model of chromium complexation is developed in a wide range of concentrations (0.001–1.2 mol/l). The results of calculations satisfactorily agree with the experimental data, which confirms the adequacy of the suggested mathematical model of the equilibrium composition of an aqueous chromium sulfate solution. The nature of “green” modification of Cr2(SO4)3 is established. This modification occurs in its diluted solutions (c < 0.1 mol/l) due to predominant polynuclear chromium hydroxo complexes, whereas in the concentrated solutions (c > 0.1 mol/l), it forms due to prevailing chromium sulfate complexes. The diagram was plotted that shows the regions with different prevailing forms of the complexes in the equilibrium system H2O–Cr2(SO4)3 at different concentrations and pH and explains the experimental data on the basis of some physicochemical properties (electric conductivity, viscosity, light absorption) of chromium sulfate solutions within a wide range of concentrations.

Crystals of [Cu(DAF)(H2O)]BF4(I) and [Cu(DAF)(ClO4)] (II) (DAF is diallyl formamide) were synthesized by an alternate-current electrochemical method, and their structures were determined (MoK αradiation, 1247 and 859 independent reflections with I≥ 2σ(I ), R= 0.043 and 0.032 for Iand II, respectively). The complexes crystallize in space group P21/n, Z= 4. For I, a= 10.782(3) Å, b= 12.096(5) Å, c= 9.185(3) Å, γ = 103.62(3)°, and V= 1164.2(7) Å3; for II, a= 10.064(3) Å, b= 10.753(6) Å, c= 10.002(3) Å, γ = 87.52(4)°, and V= 1081.4(8) Å3. The copper atom in structures Iand IIcoordinates both C=C bonds in one DAF molecule and oxygen atom of the amide group of another DAF molecule, as well as an oxygen atom of H2O (in I) or ClO4(in II) in the axial position. The uncommon behavior of the anions in structures Iand IIis explained by their different values of Pierson hardness.

Calorimetric titration was used to obtain standard thermodynamic characteristics of zinc(II) tetratert -butyl-phthalocyaninate interaction with electron-donor ligands in benzene. The formation of molecular complexes of Zn(t-Bu)4Pc with ligands (hexamethylphosphoramide, pyridine, piperidine, and morpholine) was found to be greatly affected both by the electron-donor and polarization properties of the coordinated ligands, as well as by the solvation effect of a medium. It was shown that the formation of thermodynamically stable molecular complexes of zinc(II) tetra-tert -butyl-phthalocyaninate with the electron-donor solvents (with stability constant Ks> 104) favors the formation of α-polymorphic modification of a metal phthalocyaninate during its crystallization from a given solvent.