The first crystallographically-characterised Cu(II) xanthate
Abstract The copper(II) xanthate Cu(S2COEt)2·TMEDA (1) (TMEDA = N,N-tetramethylethylenediamine) has been synthesised and is the first structurally-characterised xanthate of copper in the + 2 oxidation state. 1 has an octahedral cis, cis, cis-ligand arrangement about the metal, in which xanthate chelation is markedly asymmetric. Both bulk thermal decomposition and film growth by aerosol-assisted chemical vapour deposition (AACVD) using 1 as precursor lead to the formation of Cu2S.
Two new isomeric copper(II) complexes: Syntheses, spectroscopic characterization, single crystal X-ray structure determination and packing analyses of [Cu(L1/L2)2 (TEMED)], where L1 = 4-chloro-2-nitrobenzoate, L2 = 5-chloro-2-nitrobenzoate and TEMED = N,N,N′,N′-tetramethylethylenediamine
Abstract Two new copper(II) complexes [Cu(L1)2(TEMED)] (1) and [Cu(L2)2(TEMED)] (2) (L1 = 4-chloro-2-nitrobenzoate, L2 = 5-chloro-2-nitrobenzoate, TEMED = N,N,N′,N′-tetramethylethylenediamine) have been obtained by the addition of TEMED to hydrated Cu(II) benzoates, in methanol–water (4:1, v/v) mixture. The newly synthesized complexes have been characterized by elemental analyses, spectroscopic techniques (UV–Vis, FT-IR, EPR), magnetic moment determination, thermogravimetric analyses, and single-crystal X-ray diffraction analysis. Both complexes 1 and 2 adopt monoclinic crystal structures (space group C2/c, Z = 4) and exhibit a distorted square planar coordination geometry around Cu(II) centers. Detailed packing analyses of complexes 1 and 2 have revealed that C–H⋯π interactions in complex 1 and C–Cl⋯π interactions in complex 2 stabilize the crystal lattice. In addition, the structures are influenced by weak C–H⋯O hydrogen bonding intermolecular interactions involving both nitro and carboxylate O atoms. EPR measurements showed the presence of different environment around Cu2+ in 1 and 2.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.