Electrophilic binuclear methylpalladium(II) complexes: Copolymerization of alkenes and carbon monoxide

Reaction of [PdMe2(mu -pyd)](2) (pyd = pyridazine) with the bis(bidentate) ligands R,R/S,S-trans-1, 2-C6H10(N=CH-2-C5H4N)(2), 1, or C2H4(N=CH-2-C5H4N)(2), 2, gave the binuclear dimethylpalladium(II) complexes R,R/S/S-trans-1,2-[C6H10{N=CH-2-C5H4N(PdMe2)}(2)], 3, or [C2H4{N=CH-2-C5H4N(PdMe2)}(2)], 4, respectively. Complex 3 is C-2-Symmetric. Reaction of 3 or 4 with 2 equiv of [H(OEt2)(2)] [BAr ' (4)], Ar ' = 3,5-(CF3)(2)C6H3, in acetonitrile, gave methane and the electrophilic binuclear complexes R,R /S,S-trans-1,2-[C6H10{N=CH-2-C5H4N(PdMe-(NCMe))}(2)] [BAr ' (4)](2), 5, and [C2H4{N=CH-2-C5H4N(PdMe(NCMe))}(2)] [BAr ' (4)](2), 6, by methylpalladium bond protonolysis. Complexes 5 and 6 could be converted to the acyl complexes R,R /S,S-trans-1,2-[C6H10{ N=CH-2-C5H4N(Pd(NCMe)(COMe))}(2)] [BAr ' (4)](2), 7, and [C2H4{N=CH-2-C5H4N(Pd(NCMe)(COMe))}(2)] [BAr ' (4)](2), 8, in the presence of carbon monoxide and were found to be catalyst precursors for the copolymerization of styrene or 4-methylstyrene with carbon monoxide. Copolymerization reactions catalyzed with optically pure R,R-5* and achiral 6 were carried out at room temperature and pressure to give polyketones, whose chiral microstructures are described.