Decomposition Of Metal Complexes Research Articles

The thermal decomposition of metal complexes—XV The isomers of chromium(III) chloride 6-hydrates

The thermal dissociation of the isomeric chromium(III) chloride 6-hydrates; [Cr(H 2O) 6]Cl 3, [Cr(H 2O) 5Cl]Cl 2·H 2O and [Cr(H 2O) 4Cl 2]Cl·2H 2O, was studied by thermogravimetry, DTA, reflectance spectroscopy and analysis of the pyrolysis products. All three isomers were found to dissociate in a similar manner. A possible reaction mechanism is given for the thermal dissociation reaction.

The thermal decomposition of metal complexes—VII A thermomagnetic study of the Co(III) → Co(II) reduction in cobalt(III) ammine complexes (1)

The Co(III) → Co(II) reduction reaction was studied by means of a high temperature Gouy magnetic susceptibility apparatus for the complexes: [Co(NH 3) 6]X 3 (X  Cl, Br, I, and NO 3), [Co(NH 3) 6] 2(SO 4) 3·2·5H 2O, [Co(NH 3) 5H 2O]X 3 (X  Cl, Br, I, and NO 3), [Co(NH 3) 5X]X 2 (X  Cl, Br, I, and NO 3), and [Co(NH 3) 5X]Y 2 (X and Y may be Cl, Br and I). Minimum reduction temperatures were in the 100–200° temperature range with most of them in the 150–200° range. The curves for [Co(NH 3) 5Br]I 2 and [Co(NH 3) 5Cl]I 2 had a pronounced break at 193 and 185°, respectively. Two possible reduction mechanisms are indicated for these two complexes.

Thermal decomposition of metal complexes—VI some ammine cobalt (II) complexes

The thermal dissociation of a number of cobalt (II) ammine complexes of the type, [Co(NH 3) 6]X 2 (X = Cl, Br, I, and NO 3), and [Co(NH 3) 6]SO 4, were studied by thermogravimetry, differential thermal analysis, and gas evolution analysis. The thermal dissociation of these complexes involved intermediate ammine complexes containing lower ammonia to cobalt ratios. For the chloride and bromide complexes, the dissociation sequence was: [Co(NH 3) 6]X 2 → [Co(NH 3) 2]X 2 → [Co(NH 3)]X 2 → CoX 2. The stoichiometry of the dissociation of [Co(NH 3) 6](NO 3) 2 was: 9[Co(NH 3) 6 (NO 3) 2 → 3Co 3O 4 + 30NH 3 + 36H 2O + 17N 2 + 4NO + 2N 2O.

Thermal decomposition of metal complexes—III: Stoicheiometry of the thermal dissociation of some hexamminecobalt (III) complexes

The stoicheiometry and probable decomposition sequence for the thermal dissociation of [Co(NH 3) 6]X 3, where X is Cl, Br, NO 3 and [Co(NH 3) 6] 2(SO 4) 3·2·5H 2O, are presented. Differential thermal analysis and gas evolution curves are presented for each of the complexes. The data shows that the reduction of Co(III) → Co(III) is due to ammonia, forming NH 4X(X = Cl, Br or SO 4) and nitrogen. No free halogen could be detected. Due to the presence of both oxidizing and reducing groups, [Co(NH 3) 6](NO 3) 3 decomposed in a different manner than the other three compounds.

The thermal decomposition of metal complexes—II Some ammine and ethylenediamine complexes of nickel (II)

The thermal dissociation of some ammine and ethylenediamine complexes of nickel (II) were studied by the techniques of DTA, TGA, and GE. The ammine complexes, [Ni(NH 3) 6]X 2 (where X = Cl, Br, NO 3 and SO 4), dissociated in two steps, giving the intermediate complex, [Ni(NH 3) 2]X 2 (except NO 3). The tris(ethylenediamine)- complexes, [Ni(en) 3]X 2 (where X = Cl, Br, I, NO 3, SO 4), lost the ethylenediamine step-wise, but not as distinctly as in the hexammine-complexes. The order or increasing thermal stability for the [Ni(NH 3 6]X 2 type complexes was: NO 3 < Cl < SO 4 < Br; for the [Ni(en) 3]X 2 type complexes, the order was: Cl < Br = NO 3 < I < SO 4. The thermal dissociation process for all of the complexes is discussed in detail.