Noninnocent Behavior of a (3-Imino)indol-2-yl Ligand in Metal Complexes

Abstract

The redox noninnocence of conjugated imino-alkenyl anions has been disclosed in bis ((3-imino)indol-2-yl)iron complexes. A charge-neutral bis((3imino)indol-2-yl)iron(II) complex, abbreviated as [Fe(C-N) 2 ], was synthesized from the salt elimination reaction of FeCl 2 with 2 equiv of 2] can further react with 1 equiv of Li to form the one-electron-reduced complex Li[Fe(C-N) 2 ]. Single-crystal X-ray diffraction studies, solution magnetic susceptibility measurements, EPR, and 57 Fe Mossbauer spectroscopy, in combination with theoretical studies, revealed that both complexes are high-spin iron(II) complexes and that [Fe(C-N) 2 ] features two closed-shell monoanionic (3-imino)indol-2-yl monoanion ligands, whereas Li[Fe(C-N) 2 ] has one closed-shell monoanionic ligand and one open-shell (3-imino)indol-2-yl radical dianion ligand. An attempt to prepare the dilithium salt of the ligand radical anion by interacting 2-Li-1-(2′-(CH 2 ) 4 NCH 2 CH 2 )-3-(2′,6′-Pr i 2 C 6 H 3 NCH)C 8 H 5 N) with Li led to the isolation of a ligand degradation product.

Carbene Radicals in Transition-Metal-Catalyzed Reactions

“…These complexes exhibit high magnetic moments and are both high-spin complexes featuring a M II L •‑ configuration. Other examples of radical NHC complexes were also reported by the groups of Frenking, Enders, Wang, and Apeloig …”

“…Other examples of radical NHC complexes were also reported by the groups of Frenking, Enders, Wang, and Apeloig. 43 …”