Interaction of Nickel(0) Complexes with Allyl Carboxylates, Allyl Ethers, Allylic Alcohols, and Vinyl Acetate. ?-Complex Formation and Oxidative Addition to Nickel Involving Cleavage of the Alkenyl-Oxygen Bond

Article abstract of DOI:10.1021/ja00413a014

Interaction of various allylic compounds with bis(1,5-cyclooctadiene)nickel, Ni(cod)2, in the absence and presence of tertiary phosphines, causes cleavage of allyl-oxygen bonds.Allyl acetate reacts with Ni(cod)2 to afford a mixture of Ni(η³-C3H5)2 and Ni(OCOCH3)2 presumably through an intermediate, allylnickel acetate, followed by its disproportionation.Similar reactions in the presence of tertiary phosphine ligands, PR3 (triphenylphosphine (PPh3), ethyldiphenylphosphine (PEtPh2), tricyclohexylphosphine (P-c-Hx3)), give Ni(η³-C3H5(OCOCH3)(PR3) (1-3).Allyl formate can be catalytically converted into propylene and CO2 at 25 deg C by a Ni(cod)2-PPh3 mixture.A reaction of allyl phenyl ether with a mixture of Ni(cod)2 and PPh3 at 30 deg C also leads to cleavage of the C-O bond to yield Ni(η³-C3H5)(OC6H5)(PPh3) (4).Complexes 1-4 react with morpholine to produce N-allylmorpholine in 65-82percent yields.On the other hand, similar reactions of diallyl ether with mixtures of Ni(cod)2 and phosphine ligands do not cause C-O bond cleavage under mild conditions and yield complexes formulated as Ni(?-diallyl ether)(PR3) (PR3 = PPh3, P-c-Hx3) (5 and 6).Allylic alcohols RCH=CHCH2OH (R = H, CH3, C6H5) are dismutated into RCH=CHCH3, RCH=CHCHO, and H2O on interaction with mixtures of Ni(cod)2 and phosphines at 30-50 deg C.The mixture of Ni(cod)2 and PPh3 serves as a catalyst for the allylation of morpholine by allyl alcohol.The C-O bond in vinyl acetate is also cleaved on interaction with Ni(cod)2 alone or mixtures of Ni(cod)2 and phosphines.Complexes 1-6 are characterized by elemental analysis and spectroscopy (IR and NMR).As for the mechanism of the C-O bond-cleavage reaction of allyl-oxygen compounds, one involving coordination of the allylic compound to Ni through the C=C double bond followed by a bond rearrangement involving C-O bond cleavage is proposed.