Synthesis and Catalysis of Redox‐Active Bis(imino)acenaphthene (BIAN) Iron Complexes

Abstract

Abstract Reactions of various substituted bis(imino)acenaphthenes (R‐BIANs) with FeCl 2 (thf) 1.5 afforded the tetrahedral complexes (R‐BIAN)FeCl 2 ( 2 ) from bulky α‐diimines and the octahedral complexes [Fe(R‐BIAN) 3 ][FeCl 4 ] 2 ( 3 ) from less bulky ligands. The driving force for the formation of complexes 3 is the high ligand‐field stabilization of the low‐spin Fe II center. The two sets of complexes exhibit distinct charge‐transfer band intensities and redox activities. (R‐BIAN)FeCl 2 complexes showed reversible ligand‐centered reductions at −0.9 V (vs. FcH/FcH + ; FcH: ferrocene); further reduction led to decomposition. Irreversible oxidations were observed at 0.2 and 0.4 V, associated with a reduction at −0.4 V, as well as a ligand‐centered redox event at 1.0 V. First applications of the Fe(BIAN) complexes to hydrogenations of alkenes indicated good catalytic activity under mild conditions.