o-Diarylphosphinoferrocene Sulfonate Palladium Systems for Nonalternating Ethene–Carbon Monoxide Copolymerization

A series of ferrocene-derived o-diarylphosphino/sulfonate ligands were prepared. Treatment of the o-diphenylphosphinoferrocene sulfonic acid (2a) with (allyl)PdCl dimer and sodium carbonate as the base gave the corresponding chelate (Fc-O,P)Pd(π-allyl) complex 7a (as a mixture of two isomers). In the presence of pyridine instead of Na2CO3 the analogous reaction yielded the square-planar (Fc-O,P)Pd(Cl)pyridine complex 8a. Both systems were characterized by X-ray diffraction. Reaction of the series of three differently −P(aryl)2-substituted (Fc-O,P)H ligands with PdMe2(tmeda) gave the respective (Fc-O,P)PdMe(pyridine) derivatives (11). All three examples 11a,b,c and one precursor complex, [(Fc-O,P)PdMe]2(tmeda) (10a), were characterized by X-ray diffraction. The ligand system o-bis(o-anisyl)phosphinoferrocene sulfonic acid (2b) formed an active catalyst for ethene/CO nonalternating copolymerization upon treatment with Pd(OAc)2 in methanol. Up to ca. 25% extra ethene incorporation was obtained at an ethene/CO partial pressure ratio of ca. 10:1. This catalyst system and its equivalent derived from the preformed (Fc-O,P)PdMe(pyridine) precursor complex (11b) showed reasonable catalyst activities under these conditions.