Bidentate ferrocenylphosphines and their palladium(II)dichloride complexes — X-ray structural and NMR spectroscopic investigations and first results of their characteristics in the Pd-catalysed cooligomerisation of 1,3-butadiene with CO2

The chiral 1,1′-bis(di(+)-menthylphosphino)ferrocene (dmenpf, 1b) and achiral 1,1′-bis(diisopropylphosphino)ferrocene (disoppf, 1a) were prepared from the corresponding tertiary chlorophosphines 2b and 2a and the dilithiated ferrocene–TMEDA complex as analytically pure crystals. The synclinic eclipsed conformation of the Cp rings and the Cp(1)FeCp(1)′ angle in 1b was determined to be 175.0(2)° by X-ray structure analysis. With H2[PdCl4] 1a forms the bimetallic complex (disoppf)PdCl2 (3a). In contrast to the structure of the free ligand disoppf (1a), the X-ray structure of 3a and the NMR spectra in solution as well as in the solid state show that the P atoms are chemically and magnetically equivalent. The conformation of the Cp rings converts from an eclipsed to a staggered conformation. The ferrocene-based ligands show significant activity in the Pd-catalysed cooligomerisation of 1,3-butadiene with CO2