On the thermal decompositions of the trivalent trioxalato complexes of Al, Cr, Mn, Fe and Co

Abstract

The thermal decompositions of the complexes K-3[M(ox)(3)]. 3H(2)O (M=Al, Cr, Mn, Fe, Co; ox=C2O42-) were studied. Dehydration of the complexes occurs up to 200 degreesC, this being a three-step process for M=Al, Cr, Mn and Co, and a two-step process for M=Fe. Decomposition of the dehydrated complexes proceeds in several steps. For M=Al, Cr and Fe, the decomposition takes place with the evolution of CO, whereas for M=Mn and Co the decomposition of the oxalate ligand yields solid C besides CO. The temperature of CO liberation decreases in the series Cr lt Al lt Co lt Mn lt Fe. For M=transition metal, this trend can be explained by the fact that the strength of the C-C bond in the oxalate ligand decreases in the series Cr lt Co lt Mn lt Fe.