REACTIVITY OF TRANSITION-METAL-MODIFIED, KEGGIN-TYPE HETEROPOLYCOMPLEXES IN THE HOMOGENEOUS OXIDATION OF CYCLOHEXANE AND ADAMANTANE

The oxidation of cyclohexane and adamantane catalyzed by Keggin-type t ransition-metal-containing heteropolycomplexes (TMC-HPCs) is reported. The reactions were carried out at 20 degrees C in CCl4 or in CH2Cl2 a s reaction solvent in the presence of t-butylhydroperoxide (t-BuOOH) a s oxidizing agent. A radical chain mechanism of oxidation by t-BuOOH i n the presence of molecular oxygen is proposed for all complexes teste d, involving a R-H hydrogen atom abstraction by an intermediate active form of the TMC-HPC. Under the examined conditions molecular oxygen w as necessary to initiate the reaction, The preparation of Co(II), Fe(I II) and Cr(III)-HPC samples and their composition under reaction condi tions are also discussed, based on P-31-NMR and W-VIS absorption spect ra. (C) 1997 Elsevier Science B.V.