Ferrate( ii ) complexes with redox-active formazanate ligands

Abstract

Mono(formazanate) ferrate( ii ) complexes are described that show ligand-based redox reactions, and facile exchange of the halides to a cationic derivative.

The synthesis of mono(formazanate) iron complexes is described. In the presence of tetrabutylammonium halides, salt metathesis reactions afford the ferrate( ii ) complexes [Bu 4 N][LFeX 2 ] (L = PhNNC( p -tol)NNPh; X = Cl, Br) in good yield, and the products are characterized in detail. The high-spin ferrate( ii ) complexes show cyclic voltammograms that are consistent with reversible, ligand-based one-electron reduction. The halides in these ferrate( ii ) compounds are labile, and are displaced by 4-methoxyphenyl isocyanide (4 equiv.) as evidenced by formation of the low-spin, cationic octahedral complex [LFe(CNC 6 H 4 ( p -OMe)) 4 ][Br]. Thus, a straightforward route to mono(formazanate) iron( ii ) complexes is established.