Alkenes, photocatalytic oxidations

Most of the photocatalytic oxidations concern aliphatic and aromatic alkanes and alkenes derivatives, and the selective oxidation of alcohols to carbonyls. 

Another direction has been to develop heterogeneous applications of diruthenium paddlewheels [97]. By using multitopic carboxylate ligands, for example, 1,4-benzenedicarboxyate, RUj tetracar-boxylates are assembled into microporous networks. Interesting applications such as the catalytic hydrogenation of alkenes, the oxidation of primary aliphatic alcohols, and photocatalytic hydrogen production from water have been reported [98-101]. 

The photocatalytic hydrogenation of alkenes and dienes by Group 6 metal carbonyls has been investigated in LNG solvents [15]. Photolysis of trans-[M(C0)4(C2H4)2] (M = Cr, Mo, W) in liquid xenon doped with H2 leads to formation of mer-[M(CO)3(C2H4)2(q -H2)] and ds-[M(CO)4(C2H4)(q -H2)]. The q -H2 complexes for M = Cr and Mo are much less stable than those for M = W. The evidence supported -coordination of H2 rather than oxidative addition to give dihy-... 

Photocatalytic decomposition of water over various metal oxides to H2 and O2 is of current interest, representing an approach to the utilization of solar energy. This catalytic system catalyzes C—C bond fission and, to a lesser extent, the hydrogenation of multiple bonds. Titania220,221 and its binary oxides222 have been studied most in the hydrogenation of simple alkenes (ethylene, propylene and butenes). This photohydrogenation activity is,... 

It is now accepted that alkene hydrosilylation catalyzed by several systems occur by the modified Chalk-Harrod medTanism. Wrighton s studies on tlie insertion of ethylene into the M-Si bond of (CO) CoSiMe3 led to die conclusion that this photocatalytic process occurs by the mechanism in Scheme 16.8. Conversion of the p-silylalkyl product of insertion to the free organosilane is thought to occur by a sequence of oxidative addition of silane... 

It was also possible to set up a photocatalytic reaction where singlet oxygen oxidation of cyclic alkenes was controlled by the capsule via interaction with water-soluble Rose Bengal (RB) or insoluble dimethylbenzil (DMB) as sensitizers. All the alkenes provided quaternary 2 2 capsular self-assembled structures with the oxidation product distribution related to the position assumed in the cavity. The same reaction in acetonitrile without host led to a complex mixture of hydroperoxides (Figure 25). 

Photocatalytic Hydrogenation of Alkenes to Alkanes in Alcoholic Suspensions of Palladium-Loaded Titanium(IV) Oxide Without the Use of Hydrogen Gas... 

Imamura K, Okubo Y, Ito T, Tanaka A, Hashimoto K, Kominami H (2014) Photocatalytic hydrogenation of alkenes to alkanes in alcoholic suspensirms of palladium-loaded titartium (IV) oxide without the use of hydrogen gas. RSC Adv 4 19883-19886... 

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