such as high yields of the desired aromatic carboxylic acids in the range of 96 to 98 weight and are at the same time easily separated from the reaction products by simple filtration processes this avoids the tedious process of catalyst recovery characteristic of prior art processes and also eliminates the presence of toxic elements such as cobalt manganese and nickel in the waste effluent from the process processes utilizing these novel solid catalysts are hence environmentally more beneficial representative of the organometallic cluster complexes of cobalt and manganese of the present invention are comn 2 o ch 3 coo 6 co 2 mn o ch 3 coo 6 comn 2 o ch 3 coo y pyridine z co 2 mn o ch 3 coo y pyridine z where y z 9 etc it was also found that the organic ligands in the above mentioned organometallic cluster complex namely the acetate and pyridine lixands can be replaced by other suitable organic moieties the critical active site ensemble responsible for the high yields of aromatic carboxylic acids in the oxidation of the alkyl aromatic compounds was the heterometallic cluster complex containing both cobalt and manganese while the exact origin of this enhancement effect is not known in detail it is believed that multimetallic clusters of transition metal ions are better able to activate dioxygen o 2 than monometallic and monomeric ions the common prevalence of such heteronuclear multimetallic clusters in the o 2 activating enzymatic oxygenase catalyst systems supports such.