Synthesis and polymerization performance of Pd^II complexes of new 2-hydroxyethyl-substituted diphosphane ligands

We have synthesized a new diphosphane ligand, 1,3-bis[(2-hydroxyethyl) (phenyl)phosphanyl]propane (2*) (*: mixture of meso- and racemic diastereoisomers), and its corresponding neutral dichloro palladium(II) (3*), diiodo palladium(II) (4*), and dicationic diacetonitrile palladium(II) ditetrafluoroborate (5*) complexes. Separation of the 4 rac and 4 meso diastereoisomers was achieved by column chromatography and subsequent crystallization. Assignments of the particular complex geometries of 3 meso and 4 rac were facilitated by single-crystal X-ray diffraction analysis. After activation with MAO, complex 3* exhibits superior activity in the homopolymerization of 2-norbornene relative to that of the dichloro Pd ^II derivative of 1,3-bis(diphenylphosphanyl)propane (dppp). Compound 5* and the dppp-analogue possess similar catalytic potentials in ethylene/CO copolymerization experiments. Applying complex 5* to propylene/CO copolymerization leads to highly regio- and predominantly stereo-regular polyketone materials.