Stereoelectronic and Catalytic Properties of Chiral Cyclometalated Phospha-palladium and -platinum Complexes

The stereoelectronic properties of
palladium­(II) and platinum­(II)
complexes containing ortho-metalated (1-(diphenylphosphino)­ethyl)­naphthalene
were examined by X-ray crystallography in the solid state and by NMR
spectroscopy in solution. The studies revealed that the aromatic carbon
induced a significantly stronger electronic trans-influence than the phosphorus donor within the same five-membered
chelate. Both the organopalladium and organoplatinum chelate complexes
were formed with classical hard oxygen and soft phosphorus donor atoms.
Computational studies further confirmed the observations in the solid
state and solution that the C–metal bond in the trans C–Pt–O moiety has a stronger π-character than
that in the trans C–Pt–P moiety. Both
organometallic units are efficient catalysts for the asymmetric P–H
addition reaction. They showed almost identical efficiency in dichloromethane,
but their reactivity in THF is markedly different.