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Journal of Thermal Analysis and Calorimetry
Authors: Edward Krzyżak, Alina Wojakowska, Andrzej Wojakowski, and Marek Wołcyrz

Abstract  

Phase diagram for the system CuBr–LiBr was determined by differential scanning calorimetry and X-ray powder diffraction. The system exhibits a significant solid solubility of the components, especially LiBr in the respective polymorphic modifications of CuBr. Another feature of the system CuBr–LiBr is the occurrence of five invariant three-phase equilibria, which have been assigned to one eutectic (684 K), one peritectoid (668 K), and three eutectoids (679, 645, and 521 K). From the experimental results, formation of a compound LiCuBr2, at 521 K is discerned.

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Abstract  

The phase diagram for the CuBr−TlBr system was investigated using the differential thermal analysis completed by the X-ray powder diffraction data. Three intermediate phases were found: Tl2CuBr3 (stable from room temperature up to 234°C where decomposes in the solid state), Tl3Cu2Br5 (stable between 168°C and its incongruent melting point 262°C) and a nonstochiometric δ phase (centered about 75 mol% CuBr and stable above about 240°C).

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Abstract  

Thermal analysis on two new heterometallic sulfide clusters, [PPh4]2[WS3(CuBr)3]2 and [PPh4]2[MoS3(CuBr)3]2 (where PPh4=tetraphenyl phosphonium, =pentamethylcyclopenta- dienyl), was carried out using a simultaneous TG-DTA unit in an atmosphere of flowing nitrogen and at various heating rates. Supplemented using EDS method, their thermal behavior and properties, together with the composition of their intermediate product, were examined and discussed in connection with their distinctive molecular structure as a dianion, which provided some theoretically and practically significant information. Both clusters decomposed in a two-step mode, but without a stable new phase composed of Mo/W-Cu-S formed during their decomposition process as we expected. Based on TG-DTG data, four methods, i.e. Achar-Brindley-Sharp, Coats-Redfern, Kissinger and Flynn- Wall-Ozawa equation, were used to calculate the non-isothermal kinetic parameters and to determine the most probable mechanisms.

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The phase diagram of the SnBr2-CuBr system was determined by the method of thermal analysis. One intermediate compound, CuSn5Br11, melting congruently at 218.7 °C, was found.

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Differential scanning calorimetric measurements have been carried out for Cul, CuBr, Agl, Ag2S, NaNO2, NaNO3 and KSCN. First-order phase transformations occur with the compounds Cul, CuBr, Agl and Ag2S; NaNO2, NaNO3 and KSCN exhibit λ-type transformations. The enthalpy changes due to phase transitions have been determined. Thermal hysteresis exhibited by these compounds have been examined in the light of their change in unit cell volumes.

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Journal of Thermal Analysis and Calorimetry
Authors: H. Langfelderová, D. Makáová, and V. Jorík

Abstract  

Thermal decomposition of [Cu4O(Cl+Br)6(OPPh3)4], starts at temperatures about 200°C. The decomposition proceeds in several steps. The intermediate formed in the first decomposition step (weight loss 2–4%) is a new crystalline phase with slightly different structure but with preserved central unit Cu4O. The only crystalline phases found in the further decomposition products was CuBr in all cases when the bromine atoms were present, the presence of CuCl was only observed at the decomposition of the hexachlorocomplex.

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Reactions of divalent transition metal halides with 3,5-dimethyl-1-(hydroxymethyl)-pyrazole

Part 23. Transition metal complexes with pyrazole-based ligands

Journal of Thermal Analysis and Calorimetry
Authors: V. Leovac, R. Petković, A. Kovács, G. Pokol, and Katalin Szécsényi

Abstract  

Factors determining the complex formation reaction of copper(II), nickel(II) and cobalt(II) chloride and copper(II) bromide with 3,5-dimethyl-1-(hydroxymethyl)-pyrazole (HL) has been studied. Depending on experimental conditions, complexes with different composition were obtained: [CuCl2(dmp)]2 (I), [CuCl2(dmp)2]2 (II), [CoCl2(dmp)2] (III) (dmp=3,5-dimethylpyrazole), [CuBr(L)]2 (IV), [CoCl(L)(EtOH)]4 (V) and [NiCl(L)(EtOH)]4 (VI). The compounds were characterized by FTIR spectroscopy, solution conductivity and magnetic measurements. The crystal structure of [CoCl(L)(EtOH)]4 has been determined by single crystal X-ray diffraction. The thermal decomposition of the compounds was studied and found to be continuous for all of the compounds. The desolvation mechanism of [MCl(L)(EtOH)]4 (M=Co(II), Ni(II)) is explained on the basis of the route of complex formation of CoCl2 with HL.

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Journal of Flow Chemistry
Authors: Vinay Bhaya, Ramesh Joshi, and Amol Kulkarni

The continuous-flow Meerwein arylation is demonstrated for a set of few aryl donors (anilines and m-aminoacetophenone) and specific radical acceptors. Homogeneous catalyst (CuBr in HBr and CuCl in HCl) was used to facilitate the reaction. The effect of parameters, viz., temperature, catalyst concentration, residence time, and concentration of the radical acceptor on the yield of the arylated product, was studied. The yield of the aryl derivative obtained by continuous-flow syntheses was always better than the respective experiments in batch mode. Flow synthesis allows easy variation in these parameters and thus allows going close to the maximum possible yields in a system where the relative rates of different reactions create a complex situation. Temperature plays a crucial role by affecting the rates as well as by governing the system homogeneity. The nitrogen bubbles generated in the reaction helped to avoid any channel blockage.

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[CuXL 2 ] 2 (1–4) The complexes were prepared according to published procedures [ 6 , 7 ] , in some cases slightly modified. A suspension of 0.5 mmol of copper(I) halide (49.5 mg for CuCl, 71.7 mg for CuBr) in 50 cm 3 of dry acetonitrile

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