Metallo-complexes metal center

Inorganic-organic hybrid POMs have attracted much attention because the electron and steric properties of the POMs significantly affect the catalytic properties of a metal center [88-91]. One hybrid catalyst consisted of a metallo-salen complex attached covalently to a lacunary POM [SiWn039]8- via two propyl spacers. In contrast with an usual Mn(III) salen species, the metallosalen complex modified with the POM afforded a more oxidized Mn(IV) salen-POM or Mn(III) salen cation radical-POM compound [89]. 

These mechanistic possibilities require further investigation. Some examples of how the reaction is influenced by the structure of the olefin, the catalyst, and the solvent are given. In the presence of MX(CO)(PPh3)2 (M = Rh, Ir X = Cl, I), the oxidation of a-and /3-methylstyrenes and cis- and frans-stilbenes permitted the establishment of an activity sequence dependent on the catalyst and the stucture of the olefin. The solvent effect has been studied in the Ru complex-catalyzed oxidation of styrene and methylstyrene. In the presence of a Rh or Ir complex, the oxidation of tetramethylthylene is very selective" and takes place at a faster rate than those of the less-substituted olefins. It emerges from this that a significant role is not played by the coordinative linkage between the metal center and the olefin. Examinations have also been made on the oxidation activities of metallo-porphyrins, for example, the oxidation of cyclohexene with Co and Rh porphyrins. ... 

Especially those metallo-siloxanes bearing an Si-H function at the y silicon have a high synthetic potential, since oxidative addition to electronically unsaturated metal centers gives easy access to Si-0-Si bridged binuclear metal complexes, as illustrated in Eq. 

The SiH-functionalized metallo-siloxanes, especially, of Eq. 1 exhibit high synthetic potential due to oxidative addition to electronically unsaturated metal centers giving easy access to Si-O-Si bridged dinuclear metal complexes, like la,b and 2 (Fig. 1) [4,6b]. 

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