Influence of intramolecular N–H···O–Ni hydrogen bonding in nickel(II) diphenylphosphinoenolate phenyl complexes on the catalytic oligomerization of ethylene

Nickel(II) diphenylphosphinoenolate complexes have been prepared from (ortho-HX-substituted benzoylmethylene)triphenyl phosphoranes (X=NMe, NPh) and [Ni(1,5-cod)2] in the presence of a tertiary phosphine (PPh3 or P(p-C6H4F)3). An X-ray diffraction study of the complexes 10 and 16 establishes the presence of strong intramolecular hydrogen bonding between the enolate oxygen and the N-H function, as originally found in 11. This feature favours the formation of the desired shorter-chain-length products in the catalytic oligomerisation of ethylene.