Synthesis and characterization of mixed ligand complexes of manganese-, iron-, cobalt- and nickel(II) with some disubstituted pyridines and catechol

Mixed ligand complexes of the type (NH4)(2)[M(L-1)(2)L-2]; M = Mn-II, Fe-II, Co-II or Ni-II, HL1 = 2,3-dihydroxypyridine or 2-amino-3-hydroxypyridine; H2L2 = catechol, have been synthesized. Ail the complexes have octahedral geometry. Thermal stability, order of reaction, apparent activation energy and heat of reaction have been determined. The thermal stability order with respect to metal is, Mn < Fe < Co < Ni.