Search

The key intermediate palladacycles (mono-, bi-, and tetranuclear) with phosphonate, acetate, and other counterions in C(sp2)–H phosphonation are analyzed in terms of their redox properties, mutual ...

Copper or silver-catalyzed direct C(sp2)–H/N–H electrochemical cross-coupling of phthalimide and heterocyclic arenes (2-phenylpyridine, benzo[h]quinoline, benzoxazole, and benzothiazole, etc.) for ...

This paper elucidates the redox properties and reactivity of a number of cyclometalated nickel(II) complexes in oxidation processes. Original and robust procedures for the synthesis of nickelacycles with two cyclometalated moieties and halogenated nickelacycles were developed. The complexes were studied by means of electrochemical, ESR, DFT, and single-crystal XRD methods. Notable features of the nickelacycles are unusually low oxidation potentials. Upon electrochemical oxidation the complexes produce carbon–carbon and carbon–heteroatom coupled products, the ratio of which can be tuned by the conditions applied.

The electochemical oxidation of palladium acetate or palladium perfluoroacetate in the presence of 2-phenylpyridine promotes catalytic ortho C–H substitution reactions. As possible intermediates, Pd(II) metallacycles with Pd-bound acetate, perfluoroacetate, and perfluoroheptanoate substituents have been isolated and characterized: binuclear [(PhPy)Pd(μ-OAc)]2 and [(PhPy)Pd(μ-TFA)]2 and mononuclear [(PhPy)Pd(TFA)](CH3CN), [(PhPy)Pd(TFA)](PhPy), and [(PhPy)Pd(PFH)](PhPy). The fluorinated derivatives were found to exist in solvent-dependent equilibria between mononuclear and binuclear forms. Cyclic voltammetry was used to elucidate redox properties of the palladacycles and the oxidation route to the final products.

A variety of nickel and copper complexes bearing the trifluoromethyl ligand have been prepared in order to quantify by electrochemical methods the redox potentials relative to their chloro and methyl counterparts. The effects of coordination number and geometry, as well as the oxidation state of the metal, on the relative ease with which trifluoromethyl complexes can be oxidized have for the first time been identified. In the d10 system [(NHC)Cu(X)] (NHC = N-heterocyclic carbene, X = methyl or trifluoromethyl), a single substitution of methyl for trifluoromethyl raised the oxidation potential of the organometallic complex by approximately +0.6 V versus the ferrocene/ferrocenium (Fc/Fc+) couple, a testament to the extreme electron-withdrawing properties of the trifluoromethyl ligand. The ΔEox (methyl vs trifluoromethyl) for d8 nickel complexes were of similar magnitude; however the absolute oxidation potentials were dramatically dependent on the ligand (dippe = 1,2-bis(diisopropylphosphino)ethane vs BOXAM ...

Electrochemical reduction of phosphole P-W(CO)5 complexes affords the free phospholes in good yields. This technique allows the decomplexation of a 2-ethoxy-4-keto-4,5-dihydrophosphole, which has been characterized by X-ray crystal structure analysis of its P-sulfide.