Synthesis and Electrochemistry of Copper(I) Complexes with Weakly Basic, Fluorinated, and Multicyclic Arenes

The dinitrogen complex [(N₂)Cu{Al(OR^F)₄}] (R^F = C(CF₃)₃) acts as the precursor for the synthesis of homoleptic, weakly bound Cu(I)-arene complexes with benzene, fluorinated, and multicyclic arenes. Upon dissolution of [(N₂)Cu{Al(OR^F)₄}] in benzene or the fluorinated arenes xFB (x = number of fluorine atoms, x = 1-4), the complexes [Cu(C₆H₆)_2-3]⁺[Al(OR^F)₄]^-, [Cu(xFB)_2-3]⁺[Al(OR^F)₄]^- (x = 1-3), or the ion pair [(xFB)Cu{Al(OR^F)₄}] (x = 4) form. Both the benzene and fluorobenzene complexes are also available in larger scales by oxidation of elemental copper in the respective solvents using [NO]⁺[Al(OR^F)₄]^- as an oxidant. A higher degree of fluorination of the arene ligand leads to a weaker coordination of the Cu(I) atom and thus to higher Cu⁺/Cu redox potentials in solution that reach an unprecedentedly high value of +1.5 V (!) versus the ferrocenium/ferrocene couple in pentafluorobenzene. The versatile applicability of [(N₂)Cu{Al(OR^F)₄}] as a "naked" Cu(I) source is demonstrated by complexation reactions with the multicyclic arenes anthracene and hexaphenylbenzene that yielded multiply charged cations. All complexes presented in this work were characterized by their single-crystal X-ray diffraction structures.