Novel complexes based on 2,4,8-triarylnaphthylamine [[(2,4-{3,5-(CF)CH}-8-(3,5-RCH)-CH)-N═C(H)-{3-(9-anthryl)-2-O-CH}-κ-N,O]Ni(CH)(pyridine)] (4-Py, R = Me; 5-Py, R = CF) were synthesized from 8-arylnaphthylamines which can be generated via selective lithiation, borylation, and coupling in a one-pot procedure. Due to their living characteristics in ethylene polymerization and the particularly low propensity of 5-Py for β-H elimination as reflected by a high linearity even at elevated polymerization temperatures of 60 °C, ultrahigh molecular weight polyethylene (UHMWPE) is formed in polar organic solvents (THF, diethyl ether) as a reaction medium in a controlled polymerization ( M/ M = 1.2 at M = 1.1 × 10 g mol).

Highly electron-withdrawing pentafluorosulfanyl groups were probed as substituents in an organometallic catalyst. In Ni(II) salicylaldiminato complexes as an example case, these highly electron-withdrawing substituents allow for polymerization of ethylene to higher molecular weights with reduced branching due to significant reductions in β-hydrogen elimination. Combined with the excellent functional group tolerance of neutral Ni(II) complexes, this suppression of β-hydrogen elimination allows for the direct polymerization of ethylene in water to nanocrystal dispersions of disentangled, ultrahigh-molecular-weight linear polyethylene.

The influence of the labile ligand on the rate of β-hydride elimination (BHE) for salicylaldiminato Ni(II) complexes is shown using a series of precatalysts which differ only in the labile ligand but produce polyethylenes with a range of molecular weights (M n = 466 to 100 kg mol −1 ), degrees of branching (1.7 to 7.3 branches/1000 C), and melting temperatures (from 132 to 123°C) under the same conditions. The use of a weakly coordinating solvent (diethyl ether) was able to suppress this increase in BHE. DFT studies on a related salicylaldiminato Ni(II) complex show that BHE can feasibly occur following recombination of the labile ligand with the catalyst.

The novel weakly coordinating lipophilic anion tetrakis­[3,5-bis­(pentafluorosulfanyl)­phenyl]­borate ([S-BArF 4]−) was prepared by reaction of an aryl Grignard reagent from transmetalation with boron­(III) chloride. In other routes established for the synthesis of the trifluoromethyl analogue ([BArF 4]− with ArF = 3,5-(F3C)­C6H3), the SF5 substitution resulted in a distinctly different reactivity. Na­[S-BArF 4] as a solid is stable up to >250 °C according to thermogravimetric analysis. Single-crystal X-ray analysis of the novel cationic Ni­(II) complex [Ni­(allyl)­(mesitylene)]+[S-BArF 4]− shows a tetrahedral arrangement of the aryl units at the boron center. This complex is a catalyst precursor for butadiene polymerization in heptane with high activity and 1,4-cis selectivity (≥93%). In comparison to its [BArF 4]− analogue, the polymerization activity is 2-fold higher. Electrochemical and DFT studies further underline the weakly coordinating nature of [S-BArF 4]−.

Functionalized aluminum alkyls enable effective coordinative chain transfer polymerization with selective chain initiation by the functionalized alkyl. (ω‐Aminoalkyl)diisobutylaluminum reagents (12 examples studied) obtained by hydroalumination of α‐amino‐ω‐enes with diisobutylaluminum hydride promote the stereoselective catalytic chain growth of butadiene on aluminum in the presence of Nd(versatate)3, Cp*2Nd(allyl), or Cp*2Gd(allyl) precatalysts and [PhNMe2H+]/[B(C6F5)4 −]. Carbazolyl‐ and indolylaluminum reagents result in efficient molecular weight control and chain initiation by the aminoalkyl rather than the isobutyl substituent bound to aluminum. As confirmed for (3‐(9H‐carbazol‐9‐yl)propyl)‐initiated polybutadiene (PBD), for example, by deuterium quenching studies, polymer chain transfer by β‐hydride transfer is negligible in comparison to back‐transfer to aluminum.