Electroanalytical and spectrophotometric investigations on the metal(II)–1,2-bis(diphenylphosphino)ethane–acetylacetonate system (M = Ni, Pd, or Cu) in acetonitrile

Abstract

The soft–hard mixed-ligand complexes [M(acac)(dppe)]⁺[M = Ni or Pd, acac = acetylacetonate, dppe = 1,2-bis(diphenylphosphino)ethane] have been characterized by a combination of electroanalytical and spectrophotometric measurements. These species can easily be synthesized in acetonitrile both by a ligand conproportionation reaction upon starting from the corresponding acetylacetonate and diphosphine homoleptic species and from stoicheiometric amounts of [M(dppe)₂]²⁺ and acac^–. Upon reaction of equimolar amounts of [M(acac)₂] and dppe, the same synthesis can be achieved in the case of M = Pd, while for M = Ni the ligand-exchange reaction is followed by the reduction of nickel(II) to nickel(I) and nickel(O) occurring at the expense of the displaced acac^–. The mixed-ligand complex cannot be obtained for Cu in that copper(II) is reduced to copper(I) when dppe is present. In this low oxidation state copper is unable to co-ordinate acac^– and appears to be stable as [Cu(MeCN)₄]⁺ or [Cu(dppe)₂]⁺.