Synthesis, Crystal Structure and Hydrogen Bonding of μ- Hydroxo-μ-peroxo-bis[bis(ethylenediamine)cobalt(III)] squarate

Black-brown needle-shaped single crystals of [Co2(en)4(O2)(OH)][C4O4]1.5 4H2O(en = ethylenediamine) have been prepared in aqueous solution at room temperature. Spacegroup P-1 (no.2) with a = 800.20(8), b = 1225.48(7), c = 1403.84(9) pm, = 100.282(5), =94.515(7), = 95.596(6)°. The Co3+ cations [Co(1), Co(2)] are coordinated in an octahedralmanner by four nitrogen atoms stemming from the ethylenediamine molecules and twooxygen atoms each from a hydroxo group and a peroxo group, respectively. Both Co3+coordination polyhedra are connected by a common corner and by the peroxo group leadingto the binuclear [(en)2Co(O2)(OH)Co(en)2]3+ cation. The squarate dianions, not bonded toCo3+, and the [(en)2Co(O2)(OH)Co(en)2]3+ cations are linked by hydrogen bonds forming athree-dimensional supramolecular network containing water molecules. Magneticmeasurements reveal a diamagnetic behaviour indicating a low-spin electron configuration ofCo3+. The UV-Vis spectra shows two LMCT bands ( *(O22 ) d *(Co3+)) at 274 and 368nm and the d-d transition (1A1g 1T1g) at 542 nm. Thermoanalytical investigations in airshow that the compound is stable up to 120 °C. Subsequent decomposition processes to cobaltoxide are finished at 460 °C.

COMPETITION OF OXYGEN- AND NITROGEN-DONOR LIGANDS IN THE SYNTHESIS OF COMPLEX COMPOUNDS OF COPPER WITH 2-(PHENYL-4-CHLOROPHENYLACETYL)INDANDIONE-1,3

The interaction of CuCl and 2-(phenyl-4-chlorophenylacetyl)indandione-1,3 (HL, C23H15ClO3) in a mixed organic solvent (CH3CN, C5H5N, EtOH) gave a solvated crystal complex of copper(II) of composition [Cu(C2H5OH)(L)2]•C2H5OH (I). The isolated compound was investigated by X-ray and IR spectroscopy methods. Lattice parameters of (I): space gr. P21/c, a = 14.982(1), b = 14.558(1), с = 20.608(2) Å; β= 105.176(2)°; Z = 4 (Z′=1). It is established that the structural units in the crystal structure of the obtained compounds are the neutral square-planar coordination spheres of Cu(II) with cis-oriented deprotonated indandionate ligands L. The spheres are located in the space pairwise. One molecule of EtOH is included in the internal sphere of the complex, and the second is a bridge that unites the coordination centers due to the hydrogen bonds between the hydrogen atom of the hydroxo group of the coordinated alcohol and the O-atom of the keto group of the adjacent bis-chelate. This results in a dimer structure. At the same time, in addition to ethanol, molecules of other co-solvents (CH3CN, C5H5N) do not participate in complex formation and do not form solvates. It was found that a copper(II) complex is formed from copper(I) chloride. When using copper(I) iodide as a starting compound in ethanol in the presence of pyridine the formation of the chelate with the deprotonated ligand HL is not observed.

QM/MM calculations reveal a bridging hydroxo group in a vanadium nitrogenase crystal structure

A recent crystal structure of VFe protein is revealed via QM/MM calculations to contain an hydroxo group, likely derived from water.

Cobalt Complexation with Unsymmetrical Tripodal Ligands

The reaction of the aliphatic unsymmetrical tripod [N(CH2CH2NH2)2(CH2CH2OH)], H5-1, with cobalt(II) chloride in THF yields after aerial oxidation the dinuclear complex [(H4-1)CoIII(μ-OH)CoIII(H4-1)](CoIICl4)Cl, [5](CoCl4)Cl. The trianion 53− contains two cobalt atoms triply bridged by two alkoxo groups of the singly deprotonated ligand (H4-1)− and a hydroxo group. The new ligand [N(CH2CH2CH2NH2)(CH2CH2OH)2], H4-3, providing an N2O2 donor set reacts with cobalt(II) chloride to give after aerial oxidation the hexanuclear complex [CoIII4(H2-3)4CoII2(HOMe)2Cl2(μ-OH)4], [6]Cl2, containing an unprecedented mixed-valent CoIII4CoII2 core.

Investigation of the crystallization of ZrO2 (Y2O3 3 mol%) nanopowder

The coprecipitation technique has been used to prepare ZrO2 (Y2O3 3 mol %) nanopowder. The influence of residual NH4Cl and pH value on the crystallization of ZrO2 (Y2O3 3 mol %) nanopowder have been investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), x-ray diffraction (XRD), infrared spectrometry (IR), and transmission electron microscopy (TEM) techniques. The IR spectra proved that the presence of residual NH4Cl increased the amount of the hydroxo group. This led to serious gel agglomerate and free enthalpy decrease. Therefore, the crystallization of ZrO2 (Y2O3 3 mol%) nanopowder is greatly influenced by the residual NH4Cl. While there is no residual NH4Cl, the crystallization takes place at 445 °C and is an exothermic process. On the contrary, with NH4Cl the crystallization takes place at 376 °C and is an endothermic process. However, the pH value does not influence the crystallization of ZrO2 (Y2O3 3 mol%) nanopowder.

The structure of the tetrachlorohydroxotellurate(IV) anion in KTeCl4(OH)•0.5H2O and KTeCl4(OH)

Three compounds containing the tetrachlorohydroxotellurate(IV) anion, [Formula: see text] K[TeCl4(OH)]•0.5H2O, and K[TeCl4(OH)], have been prepared. The crystal structure of K[TeCl4(OH)]•0.5H2O has been determined. The structure contains isolated square pyramidal TeCl4(OH)− anions with OH axial. Vibrational spectroscopy shows that [Formula: see text] and K[TeCl4(OH)]•0.5H2O both contain isolated anions but that, in K[TeCl4(OH)], the anion is polymerized with chloride bridging. The hydroxo group, like the fluoro group, acts to hinder coordination at the site trans to it on Te(IV). Key words: tellurium(IV) complexes, chlorotellurate(IV), X-ray structure, vibrational spectroscopy.