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Photoassisted Oxidative Addition

In the photochemical reaction between the platinum(II) complex PtMe2(phen) and isopropyl iodide, the triplet (MLCT) state of the complex initially abstracts an iodine atom to give the intermediate platinum(III) complex PtIMe2(phen). In the absence of a free radical inhibitor, the platinum(IV) product PtI(IV)Me2(phen) is that resulting from oxidative addition [Eq. (7.11)]. In the presence of the radical inhibitor 4-methoxyphenol (T), the free isopropyl radical is trapped and the final product is now Ptl2Me2(phen) (Ref. 55)  [Pg.283]

PtMe2(phen) + IIV PtIMe2(phen) + IV Ptl2(Pi )Me2(phen) (7-12) [Pg.283]

In a few cases alkyl complexes can be synthesized by the photoaddition of dichloromethane or chloroform to a low-valent transition metal complex, but the usual products from these halogen abstraction reactions are the dichloro complexes. Photoinduced oxidative addition reactions are not always the result of the generation of an excited state that is more reactive than the ground state. An alternative photochemical pathway can involve the initial dissociation of a ligand to generate a coordinately unsaturated intermediate, which is then activated toward oxidative addition of the substrate. An example of such a reaction is [Pg.283]

Intramolecular photoinduced oxidative addition reactions can also occur. For example, when the platinum(0) complex Pt(C2H4)(PPh3)2 is photolyzed at 280 nm, the product is a cyclometalated platinum(II) complex formed by intramolecular oxidative addition of the ortho carbon-hydrogen bond, followed by ethylene insertion into the intmnediate platinum(II) hydride  [Pg.283]


Successive hydrogen transfers within 60, followed by coordination of olefin and then H2 (an unsaturate route), constitute the catalytic cycle, while isomerization is effected through HFe(CO)3(7r-allyl) formed from 59. Loss of H2 from 60 was also considered to be photoinduced, and several hydrides, including neutral and cationic dihydrides of iridium(III) (385, 450, 451), ruthenium(II) (452) and a bis(7j-cyclopentadienyltungsten) dihydride (453), have been shown to undergo such reductive elimination of hydrogen. Photoassisted oxidative addition of H2 has also been dem-... [Pg.378]

Photodissociation of coordinated ligands has also lead to the synthesis of new complexes by oxidative addition to the coordinatively unsaturated intermediates as in reactions (17)—(19).85-87 These types of reactions have been invoked in transition metal complex photoassisted and photocatalyzed reactions. [Pg.65]

Oxidative Addition to Low Valent Metal Complexes. The H/D exchange and oxidative addition of aromatic compounds by low valent coordina-tively unsaturated complexes are well known. On the other hand, clear examples of the oxidative addition of saturated hydrocarbons were first reported in 1982, in which 16-e iridium(I) and rhodium(I) complexes, which are generated through the photoassisted dissociation of CO or H2 were utilized. Similar methodologies are applicable to methane activation. Thus, 16-e cyclopentadienyl iridium(I) complexes, which are generated thermally or under photolysis, easily react with methane and result in methyl hydrido complexes at relatively low temperatures (eq. (D) (2,3). [Pg.1583]

Pignatello JJ, Liu D, Huston P. Evidence for an additional oxidant in the photoassisted Fenton reaction. Environ Sci Technol 1999 33 1832-1839. [Pg.124]

Another interesting feature of the AMO photocatalysts is the effect of diluent substrates such as MgO or activated C. Addition of substrates causes an increase in the rate of photoassisted catalytic oxidation of isopropanol. A synergistic effect is clear specific amounts of diluent lead to an increase. Too much or too little diluent leads to a decrease in rate. The exact explanation of this synergistic effect is not known, however, it may related to the ability of species such as OH or adsorbed hydrocarbons and intermediates to travel back and forth across the AMO/substrate interface. There does not seem to be a correlation of rate with the surface area, acid base character, particle size or other physical/chemical properties of the substrate. [Pg.64]


See other pages where Photoassisted Oxidative Addition is mentioned: [Pg.283]    [Pg.283]    [Pg.386]    [Pg.1032]    [Pg.365]    [Pg.448]    [Pg.1236]    [Pg.175]    [Pg.355]    [Pg.377]    [Pg.382]    [Pg.1236]    [Pg.4690]    [Pg.114]    [Pg.353]    [Pg.19]   


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