POLYHEDRAL SILSESQUIOXANES AS PRECURSORS OF TAILOR-MADE HETEROGENEOUS CATALYST CENTERS .1. WATER OXIDATION

Fe-, Ni-, Cu- and Mn-polyhedral oligometallasilsesquioxanes containing (PhSiO1.5)12(MO)nL-fragments (where L = ROH, H2O; n = 6 for Fe, Ni, Mn and n = 4 for Cu; Ni 4 Fe 2- and Ni4Cu2-complexes were also used) have been used for the preparation of heterogeneous catalysts to investigate the influence of structural factors on the catalytic properties of the hydroxides of these metals. SAXS have been used for the characterization of the distribution of complexes associated in the solution and on the supports surface. It was found that the complex distribution on the carbon support (soot) is close to monomolecular. The highest O2 yields have been obtained when Fe6/C Were used as catalysts. It has been found that supports have a strong influence on the catalytic properties of supported complexes. The catalysts prepared based on the Fe6 complexes were more active than those prepared from Ni4Fe2 complexes, in which active Fe atoms are separated by inactive Ni atoms. This observation is very important for the mechanism developed by the authors. According to this mechanism it is necessary for the formation of O2 to have at least two metal ions associated with each other in active centre.