LAUSR

ABSTRACT: The [Ni(COD)2]/P P-catalysed hydroalkoxylation of butadiene to form butenyl ethers is studied mechanistically, where P P = 1,4-bis(diphenylphosphino)butane (dppb) and 1,2-bis(diphenylphosphinomethyl)benzene (dppmb). Experimental studies suggest the intermediacy of [(P P)Ni(0)(butadiene)] and [(P P)Ni(II)(allyl)] intermediates and rule out the involvement of Ni-H species. The related species [(dppb)Ni(1,4-diphenylbutadiene)], 1, and [(P P)Ni(crotyl)(Cl)] complexes 2 (P P = dppmb) and 3 (P P = dppb) have been synthesized and characterized on the basis of VT NMR spectroscopy and X-ray crystallographic studies. 2 and 3 are shown to be catalytically competent for the hydroalkoxylation reaction. Computational studies on [(dppmb)Ni(butadiene)] indicate a facile protonation that form a cationic allylic intermediate [(dppmb)Ni(-C4H7)]OMe. C-O bond formation then occurs via external attack by the solvent-stabilized methoxide nucleophile. Hydroalkoxylation proceeds with modest computed barriers of ca. 15 ...