Hydrogenation alkenes and

Addition of hydrogen atoms in the presence of a metal catalyst to double or triple bonds is known as hydrogenation or catalytic hydrogenation. Alkenes and alkynes are reduced to alkanes by the treatment with H2 over a finely divided metal catalyst such as platinum (Pt—C), palladium (Pd—C) or Raney nickel (Ni). The platinum catalyst is also frequently used in the form of Pt02, which is known as Adams s catalyst. The catalytic hydrogenation reaction is a reduction reaction. 

Finally a carbene compound with a U=C bond is Cp3U=CHPMe3.61 Various alkyl and hydrido Cp species can catalyze oligomerization of terminal acetylenes, activate C-H bonds, hydrogenate alkenes, and so on.62... 

If the MLn catalyst fragment is also chiral, then we can use one resolved enantiomer of the chiral complex as catalyst. Instead of forming two enantiomeric alkene complexes in equal amovmts, we will have diastereomeric alkene-catalyst complexes, and in principle could have unequal amounts. Once H2 is added to the face the metal was bound, we have unequal amounts of the two enantiomeric products. One enantiomer of the catalyst should preferentially give one enantiomer of the hydrogenated alkene, and the other enantiomer should give the other product. In favorable cases, enantiomeric excesses of >95% can be obtained (e.e. = amount of major isomer-amount of minor isomer / total of both isomers ). 

Reaction of 1,1-diphenylethcne with Ru3(CO)i2 affords low yields of Ru6(At6-C)(/r-CO)(CO)i3(7/ -PhCHMePh) 159, containing the hydrogenated alkene, and the spectroscopically characterized Ru6(/i6-C)( -CO)(CO)i3(7/ -PhCH=CHPh), containing the unsaturated ligand, but no linked clusters. Trace amounts of the heptanuclear species 296 ate also isolated. 

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