Highly efficient monocationic palladacycles of chelating diphosphines in C2H4/CO copolymerization

Cationic palladacycles of the general formula [(o-C6H4(CH2)N(R)(2)Pd((PP)-P -boolean AND)}][X] ((PP)-P-boolean AND=Ph2P(CH2)(3)PPh2, (PhCH2)(2)C(CH2PPh 2)(2); X = Cl, PF6, B(C6H5)(4); R = H, CH3, CH2C6H5) and [{o-(CH2)C6H4P(o-T ol)(2)Pd((PP)-P-boolean AND)}][X] ((PP)-P-boolean AND = Ph2P(CH2)(3)PPh2; X = CI, PF6) have been prepared and structurally characterized in the former case (X-ray structure analysis for X = PF6, R = CH3). They are resistant t o air and moisture, both in solution and the solid state, and represent one of the most active single-component catalyst systems for the perfectly alt ernating C2H4/CO copolymerization in aprotic solvents. Stoichiometric model reactions provide insight into the mechanism, suggesting that insertion of carbon monoxide into the carbon-palladium(II) bond initiates the catalytic cycle.