Radical salts of bis(ethylenediseleno)tetrathiafulvalene with paramagnetic tris(oxalato)metalate anions

The synthesis, crystal structure, and physical characterization of five new radical salts formed by the organic donor bis(ethylenediseleno)tetrathiafulvalene (BEST) and the paramagnetic tris(oxalato)metalate anions [M(C2O4)3]3- (M = FeIII and CrIII) are reported. The salts isolated are (BEST)4[M(C2O4)3].PhCOOH.H2O with MIII = Cr (1) or Fe (2) (crystal data: 1, triclinic, space group P(-)1 with a = 14.0999(4) A, b = 15.3464(4) A, c =19.5000(4) A, alpha = 76.711(5) degrees, beta = 71.688(5) degrees, gamma = 88.545(5) degrees, V = 3893.5(2) A3, and Z = 2; 2, triclinic, space group P(-)1 with a = 14.0326(3) A, b =15.1981(4) A, c =19.4106(4) A, alpha = 76.739(5) degrees, beta = 71.938(5) degrees, gamma = 88.845(5) degrees, V = 3824.9(2) A3, and Z = 2), (BEST)4[M(C2O4)3].1.5H2O with MIII = Cr (3) or Fe (4) (crystal data: 3, monoclinic, space group C2/m with a = 33.7480(10) A, b =12.3151(7) A, c = 8.8218(5) A, beta = 99.674(5) degrees, V = 3614.3(3) A3, and Z = 2; 4, monoclinic, space group C2/m with a = 33.659(6) A, b =12.248(2) A, c = 8.759(2) A, beta = 99.74(3) degrees, V = 3558.9(12) A3, and Z = 2), and (BEST)9[Fe(C2O4)3]2.7H2O (5) (crystal data: triclinic, space group P(-)1 with a =12.6993(3) A, b =18.7564(4) A, c = 18.7675(4) A, alpha = 75.649(5) degrees, beta = 107.178(5) degrees, gamma = 79.527(5) degrees, V = 3977.5(3) A3, and Z = 1). The structures of all these salts consist of alternating layers of the organic donors and tris(oxalato)metalate anions. In 1 and 2 the anionic layers contain also benzoic acid molecules H-bonded to the terminal oxygen atoms of the anions. In all salts the organic layers adopt beta-type packings. Along the parallel stacks the donors form dimers in 3 and 4, trimers in 5, and tetramers in 1 and 2. All the compounds are paramagnetic semiconductors with high room-temperature conductivities and magnetic susceptibilities dominated by the Fe- or Cr-containing anions.     

Cadmium(II)bis(oxalato)cobaltate(II)- pentahydrate

A mixed metal carboxylate, cadmium(II)bis(oxalato)cobaltate(II)pentahydrate, has been synthesized and characterized by elemental analysis, IR spectral, reflectance and X-ray powder diffraction studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that the compound decomposed to CdCoO3 at 370°C through the formation of an anhydrous compound at ~194°C. Finally, CdCoO₂ is generated at 1000°C. DSC study in nitrogen up to 550°C showed the formation of a mixture of CdO and Co₃O₄ as end products. The kinetic parameters have been evaluated for the dehydration and decomposition steps using four non-mechanistic equations, i.e., Freeman and Carroll, Coats and Redfern, Flynn and Wall, MacCallum and Tanner equations. Using seven mechanistic equations, the rate controlling processes of the dehydration and decomposition mechanism are also inferred. The kinetic parameters, DH and DS obtained from DSC are discussed. IR and X-ray powder diffraction studies identified some of the decomposition products. A tentative mechanism for the decomposition in air is proposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Neutron bombardment of lithium bis(oxalato) borate: LiBOB

Lithium bis(oxalato) borate (LiBOB) was neutron bombarded with a flux of 2.40 × 10¹² n cm⁻² s⁻¹ for 1, 2, 3 and 4 h. The neutron damaged LiBOB was studied by FT-IR and Raman spectroscopy as well as by DSC (Differential Scanning Calorimetry). It is shown that the neutron bombardment causes the radiolysis of the oxalate ligand of LiBOB producing boric acid. The kinetics of LiBOB radiolysis under neutron bombardment was fitted according to the pseudofirst order kinetics law using either the FT-IR data or the decomposition enthalpy data leading in both cases to a rate constant of 9.2 × 10⁻⁵ s⁻¹. Pristine LiBOB is not a paramagnetic solid but after neutron bombardement it gives a very clear and stable ESR signal attributed to trapped spins in the radiolysis products.

     

Thermal decomposition of manganese(II)bis(oxalato)nickelate(II)tetrahydrate

Summary A mixed metal oxalate, manganese(II)bis(oxalato)nickelate(II)tetrahydrate, has been synthesized and characterized by elemental analysis, IR spectral and X-ray powder diffraction (XRD) studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that the compound decomposed mainly to Mn₂O₃, MnO₂ and NiO at ca.1000°C, via. the formation of several intermediates. DSC study in nitrogen upto 500°C showed the endothermic decomposition. The tentative mechanism for the thermal decomposition in air is proposed.     

Thermal decompostion studies on nickel(II) bis(oxalato)nickelate(II) pentahydrate

The paper describes the synthesis and thermal decomposition of nickel(II)bis(oxalato)nickelate(II)pentahydrate, Ni[Ni(C₂O₄)2].5H₂O. The complex was characterized by elemental analysis, infrared, electronic, e.s.r., magnetic moment measurement and X-ray powder diffraction studies. The thermal decompostion of the complex led to NiO in air at about 338° and in nitrogen at about 720°. The activation energies (E ^*) for the dehydration and decompostion reactions in air and nitrogen were evaluated. Tentative reaction mechanisms have been suggested for the termal decompostion of the complex in air and nitrogen.

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Zusammenfassung Es wird die Synthese und thermische Zersetzung von Nickel(II) -bis(oxalato)- nickelat(II) - pentahydrat beschrieben: Ni[Ni(C₂O₄)2].5H₂O. Dieser Komplex wurde mittels Elementaranalyse, IR-Spektroskopie, ESR-Spektroskopie, der Messung des magnetischen Momentes sowie mittels Pulverdiffraktionsuntersuchungen charakterisiert. Im Ergebnis der thermischen Zersetzung entsteht NiO, in Luft bei etwa 338°, in Stickstoffatmosphäre bei ca. 720°. Die Aktivierungsenergien (E^*) der Dehydratations- und Zersetzungsreaktionen in Luft und in Stickstoff wurden ermittelt. Für die thermische Zersetzung des Komplexes in Luft bzw. in Stickstoff wurde ein Reaktionsmechanismus entwickelt.

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The authors thank the RSIC, CDRI, Lucknow for microanalysis, RSIC, NEHU, Shillong for i.r. spectra, RSIC, IIT, Madras for far i.r. spectra, RSIC, Nagpur University for thermal analysis, Dr. S. K. Datta for Forensic Science Laboratory, Guwahati, Assam for DSC and Dr. K. L. Deori of Dibrugarh University for X-ray powder diffraction photographs.     

Synthesis and thermal decomposition of cobalt(II) bis(oxalato)cobaltate(II) tetrahydrate

Cobalt(II) bis(oxalato)cobaltate(II) tetrahydrate (Co[Co(C₂O₄)] · 4H₂O) was synthesized and characterized on the basis of elemental and spectral analysis. The thermal decomposition of the complex was investigated in air and nitrogen media. In air, complete dehydration of the complex occured at 251°, followed by rapid decomposition to a mixture of CO₂O₃ and Co₃O₄ at 300°; in nitrogen, dehydration occurred at 206°, followed by decomposition to a mixture of Co and CoC₂O₄, and finally to Co + CoO, at 394° and 420°, respectively. The activation energies for the dehydration and decomposition reactions in nitrogen and air media were evaluated and a tentative reaction mechanism for the thermal decomposition of the complex was proposed.

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Zusammenfassung Das Tetrahydrat von Kobalt(H)bisoxalatokobaltat(II) wurde dargestellt und mittels Elementar- und Spektralanalyse characterisiert. Die thermische Zersetzung der Komplexe wurde sowohl in Luft- als auch in Stickstoffatmosphäre untersucht. In Luft erfolgt bei 251 °C eine vollständige Dehydratierung, gefolgt von einer schnellen Zersetzung bei 300 °C in Co₂O₃ und Co₃O₄. In Stickstoff erfolgt die Dehydratierung bei 206 °C, gefolgt von einer Zersetzung bei zunächst 394 °C in Co und CoC₂O₄, anschliessend bei 420 °C in Co und CoO. Die Aktivierungsenergien für die Dehydratierung und Zersetzung in Stickstofo- und Luftatmosphäre wurden ermittelt und für die thermische Zersetzung der Komplexe ein Reaktionsmechanismus gegeben.

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- -() ([(₂₄)₂]·4₂), - . 251 ° _{23 34} 300 °. 260 ° ₂₄, , , 394 420 °. - , .

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The authors thank the RSIC, CDRI, Lucknow for the C, H analyses and IR spectra: RSIC, IIT, Madras for the low-frequency IR spectra; RSIC, IIT, Bombay for the e.s.r. spectra; RSIC, Nagpur University for the TG and DTG measurements; and Dr. S. K. Datta of Forensic Science Laboratory, Gauhati, Assam for the DSC measurements.     

Synthesis, structural and magnetic studies of imidazolium bis(oxalato)cuprate(II)

Imidazoliumm bis(oxalato)cuprate(II) has been synthesized and its structure determined by X-ray crystallography. Variable temperature magnetic susceptibility measurements, as well as EPR and UV-vis spectroscopic studies, have been carried out. The results show that in the solid state the compound exists in a chain-like structure, with an asymmetric one-atom weak oxalate bridge joining adjacent Cu^II centres. Of the two oxygen atoms of each coordinated oxalate only one participates in bridging; thus, each oxalate ultimately achieves three-point coordination. Each of the imidazolium ions participates in two hydrogen through the N—H moieties. The compound exhibits a weak antiferromagnetic interaction (J = −0.40 cm⁻¹).EPR spectra reveal that the triplet state is appreciably populated at both room and liquid nitrogen temperatures.     

Synthesis, characterization and radiolytic properties of bis(oxalato)borate containing ionic liquids

Previously unreported bis(oxalato)borate (BOB) ionic liquids (ILs) containing imidazolium, pyridinium, and pyrrolidinium cations were prepared from the corresponding halide salts by reaction with sodium bis(oxalato)borate (NaBOB), and their properties are reported. Pulse radiolysis experiments revealed that the BOB anion scavenges solvated electrons with rate constants of 3×10⁸ M⁻¹ s⁻¹ in the ionic liquid C₄mpyrr NTf₂ and 2.8×10⁷ M⁻¹ s⁻¹ in water. This reactivity indicates that BOB ILs may be too sensitive to be used as neat solvents for nuclear separations processes in high radiation fields but may still be useful for preventing criticality while processing relatively “cold” fissile actinides.     

Kinetics and mechanism of formation of tetrachloropalladate(II) in the reactions of bis(oxalato)- and bis(malonato) palladate(II) with chloride in acid media

Summary Kinetics of formation of [PdCl₄]^2– from [Pd(ox)₂]^2– and [Pd(mal)₂]^2– has been studies in aqueous acid media in the presence of an excess of chloride ion by stopped-flow spectrophotometry. Both the complexes undergo the transformation in two well separated consecutive steps. In 0.02–0.05 M acid with 0.2 M Cl^–, Pd(AA)^2– dissociates leading to the formation of [Pd(AA)Cl₂]^2– (where AA =ox^2– or mal^2–), which in 0.1–0.6 M acid and 1 M Cl^– forms [PdCl₄]^2– in a relatively slow step. For both steps k_abs=k₀+k₂[H⁺][Cl^–]. Activation parameters corresponding to k₀ and k₂ have been determined. Results indicate that [Pd(mal)₂]^2– is much more labile to substitution than [Pd(ox)₂]^2– and for both the lability is far greater than that of [Pd(bigH)₂]²⁺ and [Pt(ox)₂]^2– reported earlier.     

Thermal studies on oxalate complexes. IV. Potassium bis(oxalato)cuprate(II) dihydrate

The dehydration and decomposition of K₂[Cu(C₂O₄)₂] · 2 H₂O have been studied using TG. The dehydration reaction gave the best fit to a second-order rate equation and has an activation energy of 411.5 ± 41.1 kJ mole^?1. Three distinct decomposition patterns were observed for the anhydrous complex. In the first case, K₂[Cu(C₂O₄)₂] decomposes to K₂CO₃ and CuO by loss of CO₂ and 2 CO. In the second case, decomposition leads to K₂C₂O₄ and Cu by loss of 2 CO₂. In the third case, the basic carbonate K₂[Cu(CO₃)_3/2O_1/2] is produced by loss of 2 CO and 0.5 CO₂. In the last case additional loss of CO₂ leads to the formation of K₂CO₃ and CuO in a separate reaction. Kinetic parameters are reported and discussed for all these reactions.     

Vibrational spectroscopy and ab initio studies of lithium bis(oxalato)borate (LiBOB) in different solvents

The effect of lithium ion coordination with the bis(oxalato)borate (BOB-) [B(C2O4)2]- anion in DMSO, PEG, PPG, and d-PPG has been studied in detail by IR and Raman spectroscopy. Ab initio calculations were performed to allow a consistent analysis of the experimental data. The main features observed in the IR and Raman spectra correspond to the presence of "free", un-coordinated, BOB- anions. Only with use of d-PPG as solvent a small amount of Li+...BOB- ion pairs were detected. The Raman spectra and the calculations together indicate that Li+ coordinates bidentately with two end-oxygen atoms of the BOB- anion. The identification of ion pairs can be used to reveal limitations of LiBOB based electrolytes. The results for LiBOB are compared with literature on other Li salts.     

Liquid extraction of noble metal ions with bis(α-aminophosphonates)

Extraction of Au(III), Pt(IV), and Pd(II) ions from hydrochloric acid media with solutions of two bis(aminophosphonates), such as N,N-bis(dipentoxyphosphorylmethyl)octylamine and N,N′-bis[[(dioctyloxyphosphoryl)methyl]butylamine], in chloroform and xylene was investigated. Both these extractants proved to be highly effective for Au(III) ions in a wide acidity range, which allows these ions to be separated from other noble metal ions with a high degree of selectivity. At the same time, Pt(IV) and Pd(II) ions cannot be separated from one another with the extractants studied. The selectivity of their separation from Fe(III), Cu(II), Co(II), and Ni(II) metal ions is, too, not high. The reasons for these results lie in the specific structural features of the extractants, which predetermine the extraction mechanism.     

Studies on Co-oxidation resistances of electrolytes based on sulfolane and lithium bis(oxalato)borate

How to exert the high-voltage performance of LiNi_0.5Mn_1.5O₄ and break through the bottleneck effect of corresponding electrolyte have become key points in advanced lithium-ion battery. Lithium bis(oxalato) borate (LiBOB) and sulfolane (SL) are chosen as additives to investigate their effects on the electrochemical performance of lithium-ion battery with LiNi_0.5Mn_1.5O₄ cathode. The quantum chemistry calculation theory shows that oxidation potential of SL–BOB^– is dramatically increased, consistent with the experimental result in CV measurement. Meanwhile, results of CV and charge–discharge cycling indicate that LiBOB and SL would be involved in the initial oxidation reaction to form an effective solid electrolyte interface film on surfaces of the cathode electrode thus enhance the cycling performance of LiNi_0.5Mn_1.5O₄/Li cells. Electrochemical impedance spectroscopy data proves that SL is beneficial to resistance decrease. All these data will become important corroborations that the combined electrolyte LiBOB and SL have good oxidation resistances.     

IR and thermal studies on a new oxomolybdenum(VI) oxalato complex

A new molybdenum(VI) oxalato complex K₄(NH₄)₁₀[Mo₁₄O₄₂(C₂O₄)₇] (PAMO) was prepared and characterized by chemical analysis, IR spectral and X-ray studies. Its thermal decomposition was studied using TG, DTA and DTG techniques. The compound is anhydrous and decomposes between 235° and 335°C in three steps. The first and the second steps occur in the temperature ranges 235°–290°C and 290–310°C to give the intermediate compounds having the tentative compositions K₄(NH₄)₈[Mo₁₄O₄₂(C₂O₄)₆] and K₂(NH₄)₂[Mo₁₄O₄₂(C₂O₄)₃], respectively, the later than decomposing to give a mixture of potassium tetramolybdate and molybdenum trioxide at 335°C. DTA also shows a peak at 530°C which corresponds to the melting of potassium tetramolybdate. An examination of the products obtained at 340° and 535°C by chemical analysis, IR spectra and X-ray studies reveals them to be identical.The authors are grateful to Dr. M. C. Jain, Head of the Department of Chemistry, for providing research facilities.