A series of metal complexes with the non-innocent N,N′-bis(pentafluorophenyl)-o-phenylenediamido ligand: twisted geometry for tuning the electronic structure

Abstract

A series of homoleptic complexes with non-innocent ligands derived from N,N′-bis(pentafluorophenyl)-o-phenylenediamine (H₂^Fpda) are reported. [Ni^II(^Fsbqdi)₂] (1), [Pd^II(^Fsbqdi)₂] (2), [Co^II(^Fsbqdi)₂] (3), and [Cu^II(^Fsbqdi)₂] (4) were synthesized, where (^Fsbqdi)¹⁻ represents a radical anion formed by one-electron oxidation of the doubly deprotonated H₂^Fpda. The oxidation states of ligands and metals in complexes 1–4 were assigned by single crystal X-ray crystallography performed at low temperatures. Complex 4 is the first Cu^II complex where both o-phenylenediamine derived ligands are monoanionic radicals. The bulky N–C₆F₅ substituents force the complexes 1, 3, and 4 to adopt a twisted geometry (intermediate between square-planar and tetrahedral). The electronic structures of the neutral compounds 1–4 and of some of their cationic and/or anionic neighboring redox states were probed using EPR and UV-VIS-NIR spectroelectrochemistry. The twisted geometry of the complexes results in considerable changes in their electronic structures compared to the well known square-planar complexes while the strongly electron withdrawing N-C₆F₅groups have a great influence on redox properties.