Heterogeneous catalysis of the air oxidation of thiols by the cobalt porphyrin intercalated into a phosphatoantimonic acid host

Cobalt porphyrin (TPPCo) has been prepared in situ as a guest molecule in the layered host material phosphatoantimonic acid, HSb(PO4)(2), here denoted SbP. The powder X-ray diffraction of the purified sample, the SbP-intercalated cobalt porphyrin (SbPTPPCo), showed the expanded interlamellar distance of SbP upon the intercalation. The electronic absorption and electron paramagnetic resonance spectra revealed the retention of cobalt porphyrin in the layered host material. The catalytic behaviour of the novel catalyst SbPTPPCo for the thiol autoxidation was investigated in quantitative detail. In our experimental conditions, the catalytic autoxidation proceeded without induction period for oxygen consumption. The intercalated cobalt porphyrin appears to be a promising catalyst owing to its good catalytic capability. No loss in activity was observed for SbPTPPCo after eight reaction cycles and a total of more than 5390 turnovers. The proposed reaction scheme for the autoxidation catalyzed by SbPTPPCo involves the formation of catalytic center of mononuclear complex by which the electron of RS- is transferred to bound and activated dioxygen. (C) 1998 Elsevier Science B.V. All rights reserved.