1,5-Cyclooctadiene catalysts, palladium complexes

As with Pd bonds, Pd H will add to unsaturated functional groups see Hydride Complexes of the Transition Metals). In the case of alkynes, the Pd H addition is cis, to give vinyl complexes. The addition of a Pd H bond to an alkene will normally generate a Pd alkyl with jS-hydrogens, which can undergo further jS-elimination. This process can lead to alkene isomerization. However, palladium complexes have not proved as useM as those of other transition metals for alkene isomerization. While 1,5-cyclooctadiene can be isomerized to 1,3-cyclooctadiene with PdCl2(PhCN)2, palladium on charcoal is a more convenient and active catalyst for this isomerization. 

Park, J.-W., Chung, Y.-M., Suh, Y.-W., and Rhee, H.-K. (2004) Partial hydrogenation of 1,3-cyclooctadiene catalyzed by palladium-complex catalysts immobilized on silica. Catal. Today, 93-95, 445-450. 

Similar studies have been reported for the complexes of norbornadiene with cuprous chloride (5) and palladium chloride 4). A complex of 1,3- and 1,4-cyclooctadiene with palladium chloride has been reported to be a useful catalyst for the polymerization of olefins (5). 

The complex [(OC)4Fe(//-PPh2)Pd( -Cl)]2 is a selective catalyst for the isomerization of 1-octene to 2-octene and the hydrogenation of 1-hexyne in the presence of 1-hexene. At 448 K, under 100 atm H2, 93% of a sample of 1-hexyne in benzene was reduced to hexene and only 3% to hexane. This is unexpected because palladium is usually an excellent catalyst for the hydrogenation of olefins. It also catalyzes the carbonylation of 1-octene under mild conditions (348 K, 50 atm). The total yield of esters was ten times greater than with [PdCl2(PPh3)2] as a catalyst. This bimetallic complex was also an effective catalyst for the carbonylation of 1,5-cyclooctadiene. ... 

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