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

摘要

Nickel(II) diphenylphosphinoenolate complexes have been prepared from (ortho-HX-substituted benzoylmethylene)tri-phenyl phosphoranes (X=NMe,NPh) and [Ni(l,5-cod)2] in the presence of a tertiary phosphine (PPh3 or P(p-C6H4F)3).An X-ray diffraction study of the complexes [NiPh{Ph2PCH…C(…O)(o-C6H4NHMe)}(PPh3)] 10 and [NiPh{Ph2PCH…C(…O)(o-C6H4NHPh)}{P(p-C6H4F)3}] 16 establishes the presence of strong intramolecular hydrogen bonding between the enolate oxygen and the N-H function, as originally found in [NiPh{Ph2PCH…C(…O)(o-C6H4NHPh)} (PPh3)] 11.This feature favours the formation of the desired shorter-chain-lengfh products in the catalytic oligomerisation of ethylene.