Hydroxo-bridged catalyst

Figure 4. Schematic of electron transfer processes for 2,6-disubstituted phenol. The ligand groups are indicated as Am and the intermediate polymer chain segments as straight lines, (a) Hydroxo-bridged catalyst (b) chloro-bridged catalyst.

In order to realize a true biomimetic industrial catalyst, it is necessary to mount the molecular catalytic sites onto surfaces. This was attempted by means of theory in a quest to extend the insights gained for a free dimer shown in Figure 4.1 by embedding the a-hydroxo-bridged dimer part onto a MgO (OH)y test rig [49]. 

Hydroxo-bridged dinuclear complexes, [Pt(P-P)(/u-OH)]2 (where P-P = DIOP, BINAP, NORPHOS, MeDUPHOS, and BPPM) as precursors have been used for the enantioselective Baeyer-Villiger oxidation of ketones (290). The platinum(O) catalyst precursor, Pt(MeDUPHOSXfrans-stylbene), catalyzes the asymmetric hydrophosphination of activated olefins (291). 

Sachtler and coworkers have proposed a plausible reason why the overexchanged Fe-MFI catalysts can possess high deNOx activity and strong hydrothermal durability. The presence of 0x0-, hydroxo- and oxygen-bridged Fe ions as much as possible is crucial for such high catalytic properties. As already... 

The formation of an Ni(I) intermediate, instead of a classical Ni(0)/Ni(II) couple, in the silane reduced Ni(cod)2/PCy3-catalysed (cod = 1,5-cyclooctadiene, Cy = cyclohexyl) cleavage of inert C-O bonds is experimentally and theoretically supported by various spectroscopic studies of the reaction mixture. In the absence of silane, the / -hydride elimination from the oxidative addition complexes leads either to Ni(0)-CO or to Ni(0)-CHO complexes. Water deactivates the Ni catalyst by forming Ni-bridged hydroxo species. ... 

Methyltrioxorhenium, CHsReOs, prepared from Re20y and (CH3)4Sn, anchored to a Si02-Al203 support is a moderately active catalyst without any additive [49], Model calculations showed that the active carbene species is formed via hydrogen atom transfer to a Re-O-Si bridging oxygen atom on the support, leading to a methylidene hydroxo derivative [50] ... 

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