Synthesis of Ni(dppe)2 and Nickel (I) Catalysts and their Ability to Catalyzed Cross-Coupling
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Nickel catalysts play a growing role in effecting a variety of cross-coupling reactions in which carbon-carbon bonds are formed. Nickel compounds have several advantages over more frequently used palladium analogues, including the ability to activate aliphatic electrophiles and to avoid β-hydrogen elimination by alkyl-metal intermediates. Both Ni(II) and Ni(0) precursors are commonly utilized, with the latter oxidation state often believed to function as the catalytically active species. In recent years, however, a number of Ni(I) compounds have also been reported to behave as apparent catalysts and, since Ni(0) and Ni(I) compounds may be readily interconvertible, it is not always clear which oxidation state forms the actual catalyst in any particular cross-coupling reaction. Ni(0) was synthesised using a zinc reduction and analyzed by NMR spectroscopy. Ni(I) was produced using comproportionation reaction and analyzed with elemental analysis. This thesis describes an investigation in which we compare Ni(0), Ni(I) and Ni(II) complexes containing phosphine and halide (Cl-, Br-, I-) ligands , in this case 1,2-bis(diphenylphosphino)ethane (dppe) for their abilities to effect e.g. Buchwald-Hartwig Amination, Heck-Mizoroki and Suzuki-Miyaura reactions with different types of substrates.