Activation and Deactivation of Neutral Palladium(II) Phosphinesulfonato Polymerization Catalysts

13C-Labeled ethylene polymerization (pre)­catalysts [κ2-(anisyl)2 P,O]­Pd­(13CH3)­(L) (1- 13 CH 3 -L) (L = pyridine, dmso) based on di­(2-anisyl)­phosphine benzenesulfonate were used to assess the degree of incorporation of 13CH3 groups into the formed polyethylenes. Polymerizations of variable reaction time reveal that ca. 60–85% of the 13C-label is found in the polymer after already 1 min polymerization time, which provides evidence that the pre-equilibration between the catalyst precursor 1- 13 CH 3 -L and the active species 1- 13 CH 3 -(ethylene) is fast with respect to chain growth. The fraction of 1- 13 CH 3 -L that initiates chain growth is likely higher than the 60–85% determined from the 13C-labeled polymer chain ends since (a) chain walking results in in-chain incorporation of the 13C-label, (b) irreversible catalyst deactivation by formation of saturated (and partially volatile) alkanes diminishes the amount of 13CH3 groups incorporated into the polymer, and (c) palladium-bound 13CH3 groups, and more general palladium-bound alkyl­(polymeryl) chains, partially transfer to phosphorus by reductive elimination. NMR and ESI-MS analyses of thermolysis reactions of 1- 13 CH 3 -L provide evidence that a mixture of phosphonium salts (13CH3) x P+(aryl)4–x (2–7) is formed in the absence of ethylene. In addition, isolation and characterization of the mixed bis­(chelate) palladium complex [κ2-(anisyl)2 P,O]­Pd­[κ2-(anisyl)­( 13 CH3)P,O] (11) by NMR and X-ray diffraction analyses from these mixtures indicate that oxidative addition of phosphonium salts to palladium(0) species is also operative. The scrambling of palladium-bound carbyls and phosphorus-bound aryls is also relevant under NMR, as well as preparative reactor polymerization conditions exemplified by the X-ray diffraction analysis of [κ2-(anisyl)2 P,O]­Pd­[κ2 -(anisyl)­(CH2CH3)P,O] (12) and [κ2-(anisyl)2 P,O]­Pd­[κ2-(anisyl)­((CH2)3CH3)P,O] (13) isolated from pressure reactor polymerization experiments. In addition, ESI-MS analyses of reactor polymerization filtrates indicate the presence of (odd- and even-numbered alkyl)­(anisyl)­phosphine sulfonates (14) and their respective phosphine oxides (15). Furthermore, 2-(vinyl)­anisole was detected in NMR tube and reactor polymerizations, which results from ethylene insertion into a palladium–anisyl bond and concomitant β-hydride elimination. In addition to these scrambling reactions, formation of alkanes or fully saturated polymer chains, bis­(chelate)pa