Preparations, NMR Spectra, and Electrochemical Properties of a (Ferrocenylcarbonyl)palladium(II) Complex and Its Derivatives with Some Chelate Groups Attached via Two Ligating Nitrogen Atoms

Abstract

Abstract Oxidative addition of (chloroformyl)ferrocene to [Pd(PPh3)4] yielded a stable acylpalladium(II) compound of [Pd(COFc)Cl(PPh3)2] (1), (Fc=ferrocenyl). Complex 1 was treated with alkali metal salts of poly(1-pyrazolyl)borates (HnBPz4−n), (Pz=1-pyrazolyl) to give complexes [Pd(COFc)(HnBPz4−n)(PPh3)], (2, n=0; 3, n=1; and 4, n=2), which retained the palladium-attached ferrocenylcarbonyl structure. Reaction of 1 with 1,10-phenanthroline (phen) afforded [Pd(COFc)Cl(phen)], whereas reaction with 2,2′-bipyridine gave [{Pd(COFc)Cl(PPh3)}2] as an isolable material. Transformation of the ferrocenylcarbonyl moiety took place to the ferrocenyl group on palladium, in chlorine-abstraction from 1 with AgClO4·H2O in CH3CN. In the temperature-dependent 1H-NMR spectra, fluxional behavior was observed for the poly(1-pyrazolyl)borate groups in 2 and 3. Electrochemical experiments were carried out for 1–4 in CH3CN using platinum working electrodes, and reversible one-electron redox-couples were detected, which were attributed to the process Fe(II)\ightleftarrowsFe(III) in the ferrocenyl moiety. Furthermore, electron-withdrawing effects of the [poly(1-pyrazolyl)borato]palladiocarbonyl moieties from the Fe centers were compared among these complexes, in relation to their redox potentials.