Reactions of neutral and ionic square-planar organometallic nickel compounds with ethylene

Article abstract of DOI:10.1016/0022-328X(92)83187-M

We have studied the reaction of ethylene with a group of complexes with R = 2,4,6-Me3C6H2, 3,5-Cl2C6H3, 2,3-Cl2C6H3, C6Cl5, or 2-MeC6H4 and L = mainly PPh3.Migratory insertion and β-elimination of vinyl or butenyl R products was observed, but only under ethylene pressure.The smallest activation energy for this reaction was observed with the complex containing 2,4,6-Me3C6H2.Detection of the hydride generated in these reactions has been attempted by formation of a metalacycle using as the starting complex.The direction of the insertion of propene into the Ni-R bond depends on the size of R.When R = mesityl, 100percent of Ni -> C2 compounds were obtained, whereas for R = 3,5-Cl2C6H3, 80percent of Ni -> C1 compounds were recovered.Many of the hydride species formed in the reactions of neutral and ionic mesityl derivatives and BF4 (L = PEt3, PMe2Ph, PPh3.P(ⁿBu)3, P(ⁱBu)3, PCy3, PBz3, dppe or PN(PPh2CH2(2-py)) with ethylene are able to catalyze the dimerization of ethylene.Bidentate ligands do not show any activity.The insertion of ethylene in the nickel-carbon bonds occurs after prior dissociation of a neutral ligand.The different selectivities are discussed.