characterization of a tricationic trigonal bipyramidal ironiv cyanide complex with a very high reduction potential and its ironii and ironiii congeners currently there are only a handful of synthetic s 2 oxoironiv complexes these serve as models for the highspin s 2 oxoironiv species that have been postulated and confirmed in several cases as key intermediates in the catalytic cycles of a variety of nonheme oxygen activating enzymes the trigonal bipyramidal complex feivotmg3tren2 1 was both the first s 2 oxoironiv model complex to be generated in high yield and the first to be crystallographically characterized in this study we demonstrate that the tmg3tren ligand is also capable of supporting a tricationic cyanoironiv unit feivcntmg3tren3 4 this complex was generated by electrolytic oxidation of the highspin s 2 ironii complex feiicntmg3tren 2 via the s 52 complex feiiicntmg3tren2 3 the progress of which was conveniently monitored by using uvvis spectroscopy to follow the growth of bathochromically shifting ligandtometal charge transfer lmct bands a combination of xray absorption spectroscopy xas mssbauer and nmr spectroscopies was used to establish that 4 has a s 0 ironiv center consistent with its diamagnetic ironiv ground state extended xray absorption fine structure exafs analysis of 4 indicated a significant contraction of the irondonor atom bond lengths relative to those of the crystallographically characterized complexes 2 and 3 notably 4 has an feiviii reduction potential of 14 v vs fco the highest value yet observed for a monoiron complex the relatively high stability of 4 t12 in cd3cn solution containing 01 m kpf6 at 25 c 15 min as reflected by its highyield accumulation via slow bulk electrolysis and amenability to 13c nmr at 40 c highlights the ability of the sterically protecting highly basic peralkylguanidyl donors of the tmg3tren ligand to support highly charged highvalent complexes