The synthesis and characterization of two neutrally charged Ni­(II) ethylene polymerization catalysts, [2-tert-butyl-6-((2,6-(3,5-dimethylphenyl)­phenylimino)­methyl)­phenolato]­nickel­(II) methyl trimethylphosphine ((CH 3 )­FI-Ni) and [2-tert-butyl-6-((2,6-(3,5-bis­(trifluoromethyl)­phenyl)­phenylimino)­methyl)­phenolato]­nickel­(II) methyl trimethylphosphine ((CF 3 )­FI-Ni) are reported. In the presence of a Ni­(COD)2 cocatalyst, these catalysts produce markedly different polyethylenes: densely branched oligomers with M w = 1.4 × 103 g mol–1 for (CH 3 )­FI-Ni vs lightly branched polyethylenes with M w = 92 × 103 g mol–1 for (CF 3 )­FI-Ni and with ∼6.5× the polymerization activity and with much greater performance thermal stability. HOESY 2D 19F,1H NMR spectra of a model Ni-ethyl compound, [2-tert-butyl-6-((2,6-(3,5-bis­(trifluoromethyl)­phenyl)­phenylimino)­methyl)­phenolato]­nickel­(II) ethyl 2,4-lutidine ((CF 3 )­FI-Ni-Et), indicate non-negligible Cβ–Hβ···F3C through-space dipolar interactions, and molecular modeling reveals that Cβ–Hβ···F­(C) distances can be as small as ∼2.61 Å during the polymerization process. Furthermore, there is no structural or spectroscopic evidence for fluorocarbon inductive effects on the structure, bonding, and reactivity of these complexes, and a catalyst with CF3 introduced β to the imino N produces only low-M w oligomers with low activity. These results argue that weak (ligand)­C–F···H–C­(polymer) interactions can significantly influence the chain transfer characteristics of these catalysts.

The synthesis, structural characterization, and ethylene polymerization properties of two neutrally charged Ni(II) phenoxyiminato catalysts are compared and contrasted. Complex FI-SO2-Ni features a −SO2– group embedded in the ligand skeleton, whereas control FI-CH2-Ni has the −SO2– replaced by a −CH2– functionality. In comparison with FI-CH2-Ni, at 25 °C, FI-SO2-Ni is 18 times more active, produces polyethylene with 3.2 times greater M W and 1.5 times branch content, and is significantly more thermally stable. The FI-SO2-Ni-derived polymer is a hyperbranched polyethylene (148 branches 1000 C–1, M W = 3500g mol–1) versus that from FI-CH2-Ni (98 branches 1000 C–1, M W = 1100g mol–1). DFT calculations argue that the distinctive FI-SO2-Ni catalytic behavior versus that of FI-CH2-Ni is associated with nonnegligible OSO···Ni interactions involving the activated catalyst.

The synthesis and characterization of two neutrally charged bimetallic Ni(II) ethylene polymerization catalysts, {2,7-di-[2,6-(3,5-di-methylphenylimino)methyl]1,8-naphthalenediolato}-bis-Ni(II) (methyl)(trimethylphosphine) [(CH(3) )FI(2) -Ni(2) ] and {2,7-di-[2,6-(3,5-di-trifluoromethyl-phenylimino)methyl]-1,8-naphthalenediolato}-bis-Ni(II) (methyl)(trimethyl-phosphine) [(CF(3) )FI(2) -Ni(2) )], are reported. The diffraction-derived molecular structure of (CF(3) )FI(2) -Ni(2) reveals a Ni⋅⋅⋅Ni distance of 5.8024(5) Å. In the presence of ethylene and Ni(COD)(2) or B(C(6) F(5) )(3) co-catalysts, these complexes along with their monometallic analogues [2-tert-butyl-6-((2,6-(3,5-dimethylphenyl)phenylimino)methyl)-phenolate]-Ni(II) -methyl(trimethylphosphine) [(CH(3) )FI-Ni] and [2-tert-butyl-6-((2,6-(3,5-ditrifluoromethyl-phenyl)phenylimino)methyl)phenolato]-Ni(II) -methyl-(trimethylphosphine) [(CF(3) )FI-Ni], produce polyethylenes ranging from highly branched M(w) =1400 oligomers (91 methyl branches per 1000 C) to low branch density M(w) =92 000 polyethylenes (7 methyl branches per 1000 C). In the bimetallic catalysts, Ni⋅⋅⋅Ni cooperative effects are evidenced by increased product polyethylene branching in ethylene homopolymerizations (∼3× for (CF(3) )FI(2) -Ni(2) vs. monometallic (CF(3) )FI-Ni), as well as by enhanced norbornene co-monomer incorporation selectivity, with bimetallic (CH(3) )FI(2) -Ni(2) and (CF(3) )FI(2) -Ni(2) enchaining approximately three- and six-times more norbornene, respectively, than monometallic (CH(3) )FI-Ni and (CF(3) )FI-Ni. Additionally, (CH(3) )FI(2) -Ni(2) and (CF(3) )FI(2) -Ni(2) exhibit significantly enhanced thermal stability versus the less sterically encumbered dinickel catalyst {2,7-di-[(2,6-diisopropylphenyl)imino]-1,8-naphthalenediolato}-bis-Ni(II) (methyl)(trimethylphosphine). The pathway for bimetallic catalyst thermal deactivation is shown to involve an unexpected polymerization-active intermediate, {2,7-di-[2,6-(3,5-di-trifluoromethyl-phenylimino)methyl]-1-hydroxy,8-naphthalenediolato-Ni(II) (methyl)-(trimethylphosphine).

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A series of dinuclear organophosphorus-bridged complexes of the general formula {(LVO(μ-O(2)PRR')}(2) [L = η(5)-cyclopentadienyltris(diethylphosphito-κ(1)P) cobaltate(III)] has been synthesized as a structural model for the industrially used vanadium phosphate oxidation catalysts. These dimeric species contain two vanadium centers in a VO(6) environment bridged by O-P-O units. These complexes have been characterized via spectral and magnetic analyses. Structural parameters have been analyzed through X-ray diffraction. The dimers generally exist in either a cis/cis-anti or retracted chair conformation in the solid state. The syntheses, structural, spectral, and magnetic data are presented and discussed here.