Selective Stabilization of the Antiisomer of (eta-3-allyl)palladium and (eta-3-allyl)platinum Complexes

A number of 2,9-disubstituted 1,10-phenanthrolines are synthesized. These are used as ligands in different cationic (eta3-allyl)palladium and -platinum complexes. It was found that while a syn configuration was by far the most stable one with the parent 1,10-phenanthroline, 2,9-substituents such as methyl, chloro, cyano, and propynyl induced a preference for the anti configuration. Since terminal nucleophilic addition to anti-eta3-allyl complexes will yield (Z)-alkenes, this observation opens up a potentially selective route to (Z)-alkenes. Using molecular mechanics calculations these effects may be rationalized.