POLYHEDRAL SILSESQUIOXANES AS PRECURSORS OF TAILOR-MADE HETEROGENEOUSCATALYST 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, M n and n = 4 for Cu; Ni 4 Fe 2- and Ni4Cu2-complexes were also used) ha ve been used for the preparation of heterogeneous catalysts to investi gate the influence of structural factors on the catalytic properties o f the hydroxides of these metals. SAXS have been used for the characte rization of the distribution of complexes associated in the solution a nd on the supports surface. It was found that the complex distribution on the carbon support (soot) is close to monomolecular. The highest O 2 yields have been obtained when Fe6/C Were used as catalysts. It has been found that supports have a strong influence on the catalytic prop erties 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 obs ervation is very important for the mechanism developed by the authors. According to this mechanism it is necessary for the formation of O2 t o have at least two metal ions associated with each other in active ce ntre.