Thermal properties of thiocyanatocopperc(II) complexes with picolines and lutidines

Vargová

Šramko

et al. 1978

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The influence of the position of the CH~ group in picoline and lutidine ligands on the degree of chemical change of the NCS groups in coordination compounds of the type Cu(NCS),,L 2 (where L = 2-, 3-and 4-picoline, and 2,3-, 2,4-, 2,5-, 2,6-, 3,4-and 3,5-1utidine) is dealt with. The most marked effect of the CHz group is found to be exerted in position 4. This effect of the methyl group on the degree of chemical change points to the mutual influence of the ligands in coordination compounds of Cu(II).In a previous paper [l] we reported the thermal properties of thiocyanatocopper(ll) complexes with all isomeric forms of picolines and lutidines. From the series of compounds studied, only Cu(NCS)2(3,5-1ut)., shows a rather similar course of thermal decomposition to that of the complex Cu(NCS)2(py)2. In these compounds the release of the heterocyclic base and the polymerization and decomposition reactions of the NCS groups take place in separate steps. The other complexes studied exhibit a very complicated thermal decomposition up to 300 ~ At higher temperatures, 300-600 ~ the DTG curves are linear and the TG curves show only a uniform loss of weight of the sample with temperature. The intermediates of thermal decomposition after the first step have non-stoichiometric composition. From the composition and some physico-chemical properties of these intermediates we may suggest the influence of the position of the methyl substituent in the ligand L on the degree of chemical changes of the NCS groups in the thermal decomposition of coordination compounds of the type Cu(NCS)2L2, (where L = 2-, 3-and 4-picoline, and 2,3-, 2,4-, 2,5-, 2,6-, 3,4-and 3,5-1utidine).

Section: Discussionmentioning

confidence: 96%

Influence of the pyridine methyl substituent position on the chemical changes of the NCS groups in the thermal decomposition of coordination compounds of the type Cu(NCS)2L2

Vargová

Šramko

et al. 1978

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Thermal properties of thio-and selenocyanatocopper(II) complexes with bipyridine and phenanthroline

Pirskij

Dunaj‐Jurčo

1988

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The paper deals with the thermal properties of complex compounds of the general formula CuL2(NCX)2 (where L = bipy or phen, X = S or Se). The phenanthroline complexes exhibit a higher thermal stability than those with bipyridine. For the latter complexes thermal decomposition begins with the release of bipyridine molecules, while for the phenanthroline complexes redox ,reactions of pseudohalogenide ligands with Cu(II) take place. The redox reactions start at a lower temperature for the selenocyanate complexes than for the thiocyanate complexes.In earlier papers, the thermal properties of thiocyanatocopper(II) complexes with pyridine and all the isomeric forms of picolines and lutidines were studied [1][2][3]. It was found that the properties of the heterocyclic ligand affect the thermal stability and the stoichiometry of thermal decomposition of these complexes. Thermal decomposition begins with the release of molecules of the heterocyclic base. The release of components stabilizing the oxidation state of Cu(II), together with increased temperature, create conditions for the commencement of redox reactions between the central atom and the thiocyanate ligand. The presence of methyl substituents on the pyridine ligand decreases the thermal stability of he thiocyanate ligands, the redox reactions are shifted to lower temperatures and they are accompanied by the release of heterocyclic ligands.Likewise, it was also found that a higher number of coordinated monodentate molecules of the heterocyclic base lowers the thermal stability of the thiocyanatocopper(II) complexes [4,5].

Thermal properties of cyanatocopper(II) complexes with pyridine, bipyridine and phenanthroline

Jorı́k

1996

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