The thermal decomposition of transition-metal complexes containing heterocyclic ligands: 2.Benzoxazole complexes

Abstract

Enthalpies of the overall decomposition reactions ▪ and of the intermediate reactions involving stepwise loss of ligand, L, where M is Mn, Co, Ni, Cu, or Cd, X is Cl or Br, and L is benzoxazole, 2-methylbenzoxazole, or 2,5-dimethylbenzoxazole have been measured by use of a differential scanning calorimeter. Specific heats of CoCl 2(2-methylbenzoxazole) 2, and CoBr 2(2-methylbenzoxazole) 2 are reported together with enthalpies of sublimation of CoCl 2(2-methylbenzoxazole) 2, CoBr 2(2-methyl-benzoxazole) 2, CoCl 2(2,5-dimethylbenzoxazole) 2 and CoBr 2(2,5-dimethylbenzoxazole) 2. Enthalpies of decomposition of benzoxazole complexes are found to be greater than those of the corresponding pyridine complexes, but less than those of the analogous benzothiazole complexes. However, the mean bond dissociation energies of the cobalt—nitrogen and cobalt—oxygen bonds in these complexes are all in the region 33±2 kcal mol −.