Synthesis, characterisation and speciation studies of heterobimetallic pyridinehydroxamate-bridged Pt(II)/M(II) complexes (M = Cu, Ni, Zn). Crystal structure of a novel heterobimetallic 3-pyridinehydroxamate-bridged Pt(II)/Cu(II) wave-like coordination polymer

The reaction of cis-[Pt(NH3)2(3-pyhaH)2]2+ (3-pyhaH = 3-pyridinehydroxamic acid) and cis-[Pt(NH3)2(4-pyhaH)2]2+ (4-pyhaH = 4-pyridinehydroxamic acid) with Cu(II), Ni(II) or Zn(II) in aqueous solution affords novel heterobimetallic pyridinehydroxamate-bridged complexes, {cis-[Pt(NH3)2(mu-3-pyha)M(mu-3-pyha)].SO4.xH2O}n and {cis-[Pt(NH3)2(mu-4-pyha)M(mu-4-pyha)].SO4.xH2O}n respectively. The crystal and molecular structure of one of these, {cis-[Pt(NH3)2(mu-3-pyha)Cu(mu-3-pyha)]SO4.8H2O}n 3a, has been determined and was found to be a novel heterobimetallic wave-like coordination polymer, the structure of which contains interlinked pyridinehydroxamate-bridged repeating units of Pt(II) and Cu(II) ions in slightly distorted square-planar N4 and O4 coordination environments respectively and extensive hydrogen-bonding through the Pt ammines and the deprotonated hydroxamate O and via the O of the SO4(2-) counterions and the H(N) of the hydroxamate moiety. Spectrophotometric and speciation studies on the other heterobimetallic systems confirm that very similar species are being formed in solution and based on elemental analysis and spectroscopic results analogous complexes are formed in the solid-state. In this paper, we report the first examples of coordination polymers incorporating both Pt(II)/Cu(II), Pt(II)/Ni(II) and Pt(II)/Zn(II) and containing pyridinehydroxamic acids as bridging scaffolds.     

237Np Mössbauer spectroscopic study on heptavalent neptunium compound

²³⁷Np Mössbauer spectrum of the heptavalent neptunium compound [Co(NH₃)₆][NpO₄(OH)₂]·2H₂O was remeasured for certification of the previous investigations. The isomer shift value of the Mössbauer spectrum showed a characteristic value for the heptavalent neptunium at 4.7K. Although the spectrum seemed to consist of two quadrupole-split peaks as previously reported byStone et al., the fitting with using two quadrupole-split peaks did not give a good agreement withStone's data.     

Platinum catalyzed reduction of uranium(VI) with hydrazine in sulfuric acid media

The process of platinum-catalyzed uranium(VI) reduction with hydrazine in sulfuric acid media has been studied. The influence of sulfuric acid and hydrazine concentrations, and temperature on the reaction rate were investigated. A new reaction mechanism is proposed. The process allows to obtain pure U(IV) sulfate solutions with concentrations of up to 0.3 mol·l^–1. Further increase of initial U(VI) concentrations is limited by the reductant solubility in sulfuric acid media.     

A correlation between isomer shifts of237Np Mössbauer spectra and coordination numbers of Np atoms in neptunyl(V) compounds

Five neptunyl(V) compounds were synthesized and studied by²³⁷Np Mössbauer spectroscopy. The isomer shifts (δ) of the Mössbauer spectra ranged from ?18.6 to ?19.1 mm/s for the compounds with Np atoms surrounded by 7 oxygen atoms (coordination number (CN) 7). On the other hand, the larger value of δ was obtained for the compound with CN 8. from the comparison of the present results with those reported on neptunyl(V) and (VI) compounds, it is concluded that there is a correlation between the δ and the CN for neptunyl(V) compounds, and the distribution of δ is narrower for neptunyl(V) compounds than that of neptunyl(VI) compounds.     

Synthesis,Crystal Structure,and Absorption Spectra of Neptunium(V) Di(acetamido) Nitrate (NpO2)(NO3)(CH3CONH2)2

The crystal structure of (NpO₂)(NO₃)(CH₃CONH₂)₂ was determined. The crystallographic data were are follows: a = 5.766(3) Å, b = 13.154(5) Å, c = 14.027(6) Å, V = 1064.0(8) ų, space group Pnma, Z = 4, _calcd = 2.804 g/cm³, R = 0.046, R _w = 0.102. The coordination polyhedron of Np is a pentagonal bipyramid whose equatorial positions are occupied by the oxygen atoms of the neighboring NpO₂ group, acetamide molecules, and of the nitrate ion. The IR and electronic absorption spectra of the compound were measured.     

Distortion of the decavanadate polyhedron and the role of hydrogen bonding in dimethylammonium decavanadate

The dimethylammonium decavanadate, [Me₂NH₂]₆[V₁₀O₂₈] · H₂O was synthesized and its crystal structure determined by X-ray diffraction. I.r. and n.i.r. spectra were also recorded. The results, compared to the reported crystal structures of decavanadates, indicate that the deformations of isolated polyhedra and their crystal lattice packing are closely related to the anion interactions both with cations and/or water (or solvent) molecules. The i.r. spectra of the relatively strongly distorted (but unprotonated) decavanadate anion are very similar to the spectrum of protonated [Me₃CNH₃]₄[H₂V₁₀O₂₈] [1], with a different distribution of hydrogen bonds. Thus the i.r. spectra of the decavanadate salts provide no evidence for protonation. In each case, the analysis of a particular decavanadate spectrum by advanced quantum chemistry calculations is needed. The near i.r. spectra of [Me₂NH₂]₆[V₁₀O₂₈] · H₂O can be helpful in gaining a better understanding of decavanadate salts structures. These results are important because of the role of decavanadate in catalysis.