In this study, we synthesized and
characterized two nickel complexes
featuring conformationally rigid bisphosphine mono-oxide ligands,
where one has an o-methoxyphenyl (Ni2) and the other has an o-(2-methoxyethoxy)phenyl
(Ni3) substituent on the PO moiety. We performed
metal binding studies using Ni3 and found that its reaction
with Li+ and Na+ most likely produced 1:1 and
1:1/2:1 nickel:alkali species in solution, respectively. The nickel
complexes were competent catalysts for ethylene homopolymerization
and copolymerization, with activities up to 3.8 × 103 and 8.1 × 10 kg mol–1 h–1, respectively. In reactions of ethylene with methyl acrylate (1.0
M), the addition of Li+ to Ni3 led to a 5.4-fold
enhancement in catalyst activity and a 1.9-fold increase in polar
monomer incorporation in comparison to those by Ni3 alone
under optimized conditions. A comparison with other nickel catalysts
reported for ethylene and methyl acrylate copolymerization revealed
that our nickel–alkali catalysts are competitive with some
of the most efficient Ni-based systems developed thus far.
A multivariate approach has been to to establish the right balance between iodine loading and pore size for catalytic oxidative dearomatizations in MIL-53 (Al) and UiO-66 (Zr) MOFs.
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