Iron(II) Corrole Anions

Reduction of [Fe(TPC)(THF)] (TPC = trianion of 5,10,15-triphenylcorrole) with KC8 generates the iron(II) corrole anion, K(THF)(2)[Fe-II(TPC)] (3a). Compound 3a represents the first example of an isolated and crystallographically characterized corrole complex of divalent iron. The compound adopts an intermediate-spin state (S = 1), displaying square-planar geometry about the iron atom. All-electron density functional theory (OLYP and B3LYP) calculations with STO-TZP basis sets indicate two essentially equienergetic d electron configurations, d(xy)(2)d(z)(22)d(xz)(1)d(yz)(1) (occupation 1) and d(xy)(2)d(z)(21)d(xz)(1)d(yz)(2) (occupation 2), as likely contenders for the ground state of [Fe-II(TPC)](-), with the optimized geometry of the former in slightly better agreement with the low-temperature X-ray structure. Solutions of 3a react with carbon monoxide to afford the low-spin (S = 0) complex, [Fe(TPC)(CO)](-), whereas introduction of oxygen at -78 degrees C leads to a putative O-2 adduct, [Fe(TPC)(O-2)](-), which decays rapidly even at low temperatures. Treatment of 3a with organic electrophiles results in formal oxidative addition to give both iron(III) and iron(IV) corrole species. With iodomethane, [Fe(TPC)Me] is produced, illustrating the first instance of alkyl ligand coordination in an iron corrole complex.