Thermoanalytical investigation of Mg(II) compounds containing SCN and heterocyclic N-donor ligands

Thermogravimetry (TG), differential thermal analysis (DTA) and other analyt ical methods have been applied to investigate the thermal behaviour and str ucture of the compounds Mg(SCN)(2)(pic)(2). 2H(2)O(I), Mg(SCN)(2)(ron)(2). 3H(2)O(II) Mg(SCN)(2)(mpc)(2). 3H(2)O(III) and Mg(SCN)(2)(caf)(2). 7H(2)O ( IV) (where pie, gamma-picoline; ron, ronicol; mpc, methyl-3-pyridyl carbama te: and caf. caffeine) in each case. Thermal decomposition of these compoun ds showed is multi-stage processes. The composition of these complexes, the solid state intermediate as well as the resultant products of thermolysis, have been identified by means of elemental analysis and compleximetric tit ration. The possible schemes of the decomposition of these complexes are su ggested. Heating of these compounds first results in the release of water o f crystallization. The loss of the volatile ligands occurs (from the TG cur ves) in two steps. The final product of the thermal decomposition in each c ase was MgS. The relative thermal stability of the complexes varied as foll ows: II < IV < III < I. The ligands (pic, ron, mpc and caf) were coordinate d to Mg(II) through the nitrogen atom of the heterocyclic ring. IR data sug gest that the SCN group is coordinated to Mg(II) through nitrogen and sulfu r in complexes I-IV. (C) 1999 Elsevier Science B.V. All rights reserved.