Several bis-chelated palladium(II)complexes, [Pd(PP)(N-N)(x)](PF6)2, containing binary combinations of diphosphine and dinitrogen ligands have been prepared and characterized. The diphosphine ligands comprise 1,3- bis(diphenylphosphino)propane (dppp), meso-2,4-bis(diphenylphosphino)pentane (meso-bdpp), rac-2,4-bis(diphenylphosphino)pentane (rac-bdpp) and 2,2'- bis(diphenylphosphinoethyl)pentane (Etdppp), while the dinitrogen ligands are either 2,2'-bipyridine (bipy; x = 1) or 1,8-naphthyridine (napy; x = 2). The structure of [Pd(meso-bdpp)(N,N'-bipy)](PF6)2 · CH2Cl2 has been determined by an X-ray structural analysis. All the Pd(II) complexes have been tested as catalyst precursors for the copolymerization of carbon monoxide and ethene in methanol solution in either autoclaves or high- pressure sapphire NMR tubes. The combination of meso-bdpp and bipy at palladium, in conjuction with both 1,4-benzoquinone and p-toluenesulfonic acid, has shown the best catalytic performance. The different catalytic activities exhibited by the stereoisomers [Pd(meso-bdpp)(N,N'-bipy)](PF6)2 and [Pd(rac-bdpp)(N,N'-bipy)](PF6)2 has been interpreted in terms of the different spatial distribution of the phenyl rings around the metal center determined by the conformation of the six-membered metallaring.
All Science Journal Classification (ASJC) codes
- Materials Chemistry