Dimerization of Ethylene by Nickel Phosphino–Borate Complexes

Trifluoroborate-functionalized
phosphine ligands react with a variety
of nickel­(II) precursors to cleanly yield a number of κ2(P,F)-bound nickel complexes, which were characterized crystallographically.
In comparison to related palladium complexes, ancillary ligands in
the nickel complexes were observed to be generally more weakly bound,
and the trifluoroborate ligands were more easily displaced by coordinating
solvents that did not cause a similar displacement in a related palladium
system. Such weaker ligand coordination resulted in a much faster
dimerization of ethylene. Experiments conducted under constant ethylene
pressure saw the suppression of the isomerization of 1-butene observed
in related palladium complexes; higher oligomers were also generated
under such conditions.

三氟硼酸基磷配体与多种镍（II）前驱体发生反应，能够纯净地生成一系列κ2(P,F)-配位的镍配合物，这些配合物已通过晶体学手段进行了表征。与相关的钯配合物相比，镍配合物中的辅助配体普遍表现出较弱的结合力，而三氟硼酸配体则更容易被不引起相关钯体系中类似位移的配位溶剂所取代。这种较弱的配体配位导致了乙烯二聚反应的显著加速。在恒定乙烯压力下进行的实验观察到，抑制了在相关钯配合物中观察到的1-丁烯异构化现象；在这样的条件下，还生成了更高阶的聚合物。