6533b871fe1ef96bd12d1176

RESEARCH PRODUCT

First copper(I) ferrocenyltetraphosphine complexes: possible involvement in Sonogashira cross-coupling reaction ?

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Preparation and characterization of the first examples of copper(I) ferrocenylpolyphosphine complexes are reported. The molecular structure of complex {P,P′,P′′-[1,1′,2,2′-tetrakis(diphenylphosphino)-4,4′-di-tert-butylferrocene]iodocopper(I)} (1) was solved by X-ray diffraction studies, and its fluxional behavior in solution was investigated by VT-31P NMR; both revealed a net triligated coordination preference of the ferrocenyl tetraphosphine Fc(P)4tBu with copper. The tetradentate ligand is an active auxiliary in Sonogashira alkynylation; therefore the general question of copper as a competitive coordination partner in the Pd/Cu-catalyzed Sonogashira reaction was raised and discussed. Electronically neutral, activated, and deactivated aryl bromides were employed for coupling with phenylacetylene with various [(Pd)/(Cu)/(tetraphosphine)] systems. The catalytic investigations shown that 1 mol % of complex 1 in combination with palladium is far more effective and selective for Sonogashira coupling than 5 mo...