Aryl(pentachlorophenyl)nickel(II) complexes. Lack of free rotation about tolyl-nickel bonds and lack of ortho effect in carbonylation

Article abstract of DOI:10.1021/ic50168a045

A series of complexes of the type trans-R(C₆Cl₅)Ni(PPhMe₂)₂ (where R = aryl) was prepared. Their ¹H NMR spectra indicate that both R = o-tolyl and m-tolyl groups are oriented perpendicularly to the nickel coordination plane. Reaction of carbon monoxide with these complexes gave, under mild conditions, R(C₆Cl₅)CO for R = aryl groups including o-tolyl but not for 2-furyl and its analogues. The o-tolyl complex was exceptionally stable toward thermal reductive elimination in tetrachloroethylene under air. Factors affecting the relative reactivities of these complexes are discussed, based mainly on the early explanation for the so-called ortho effect .