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A seriesof benzo-linked phosphine-diethyl phosphonate (P-PO) andphosphine-bis(diethyl phosphonate) (P-(PO)2) ligands andthe corresponding (P-PO)PdMe(2,6-lutidine)+and (P-(PO)2)PdMe(2,6-lutidine)+complexes were synthesized. Cationic (P-PO)PdMe(2,6-lutidine)+complexes are active for ethylene oligomerization/polymerization,with activities of 2 kg mol–1h–1for {κ2-1-PiPr2-2-P(O)(OEt)2-5-Me-Ph}PdMe(2,6-lutidine)+(3c), 125 kg mol–1h–1for {κ2-1-PPh2-2-P(O)(OEt)2-5-Me-Ph}PdMe(2,6-lutidine)+(3a), and 1470 kg mol–1h–1for {κ2-1-P(2-OMe-Ph)2-2-P(O)(OEt)2-Ph}PdMe(2,6-lutidine)+(3b). The polyethylene is highly linear, withover 80% terminal unsaturation and low (230–1890 Da) molecularweight in all cases. 3bcopolymerizes ethylene with methylacrylate, exhibiting highly selective (95%) in-chain (rather thanchain-end) acrylate incorporation. The P-(PO)2catalyst{κ2-1-P(4-tBu-Ph)(2-P(O)(OEt)2-5-Me-Ph)-2-P(O)(OEt)2-5-Me-Ph}PdMe(2,6-lutidine)+(3d) is more active for ethylene homopolymerization(2640 kg mol–1h–1), yieldinglinear, low-molecular-weight polymer (1280–1430 Da) with predominantlyinternal olefin placement. In ethylene/methyl acrylate copolymerization, 3dincorporates 2.6 mol % methyl acrylate, 60% of which isin-chain. Both 3band 3dcatalyze ethylene/acrylicacid copolymerization, albeit with low (<10 kg mol–1h–1) activities and acrylic acid incorporationup to 1.1 mol %. [ABSTRACT FROM AUTHOR]

Remote binding of B(C6F5)3 to (PPO)PdMeL (L = pyridine or lutidine) or {(PPO)PdMe}2 ethylene polymerization catalysts that contain phosphine-arenephosphinate or phosphine-arenephosphonate ligands (PPO- = [1-PAr2-2-PR'O2-Ph]-: Ar = R' = Ph (1a); Ar = Ph, R' = OEt (1b); Ar = Ph, R' = OiPr (1c); Ar = 2-OMe-Ph, R' = OiPr (1d)) significantly increases the catalyst activity and the molecular weight of the polyethylene (PE) product. In the most favorable case, in situ conversion of (1d)PdMe(py) to the base-free adduct {1d•B(C6F5)3}PdMe increases the ethylene polymerization activity from 9.8 to 5700 kg mol-1 h-1 and the Mn of the PE product from 9030 to 99 200 Da (80 °C, 410 psi). X-ray structural data, trends in ligand lability, and comparative studies of BF3 activation suggest that these allosteric effects are primarily electronic in origin. The B(C6F5)3 binding enhances the chain growth rate (Rgrowth) by increasing the degree of positive charge on the Pd center. This effect does not result in the large increase in the chain transfer rate (Rtransfer) and concomitant reduction in PE molecular weight seen in previous studies of analogous (PO)PdRL catalysts that contain phosphine-arenesulfonate ligands, because of the operation of a dissociative chain transfer process, which is inhibited by the increased charge at Pd. [ABSTRACT FROM AUTHOR]