Iron(II) Corrole Anions

Abstract

Reduction of [Fe­(TPC)­(THF)] (TPC = trianion of 5,10,15-triphenylcorrole) with KC8 generates the iron­(II) corrole anion, K­(THF)2[FeII(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 2d z 2 2d xz 1d yz 1 (occupation 1) and d xy 2d z 2 1d xz 1d yz 2 (occupation 2), as likely contenders for the ground state of [FeII(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 °C leads to a putative O2 adduct, [Fe­(TPC)­(O2)]−, 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.

Heavy-element–ligand covalence: ligand noninnocence in molybdenum and tungsten Viking-helmet Corroles

“…The Mo(4d z 2)-corrole("a 2u ") interaction evident in the HOMO−2 and LUMO (Fig. 5) is, topologically, exceedingly similar to analogous interactions involving the 3d z 2 orbital in MnCl, 23 FeCl, [10][11][12][13][14][15] FeNO, 27 and Co-PPh 3 31 corroles. Importantly, this picture was fully borne out by an examination of the 4d-based natural bond orbitals (NBOs) of the molecule.…”

“…To gain an estimate of the strength of the Mo(4d z 2)corrole •2− antiferromagnetic coupling, we optimized the corresponding ferromagnetically-coupled (S = 3/2) state of Mo[TPC]O and found its energy to be ∼0.9 eV above the ground state (for the B3LYP functional). In stark contrast, the ferromagnetically coupled states of MnCl, 23 FeCl, [10][11][12][13][14][15] FeNO, 27 and Co-PPh 3 31 corroles were invariably found to occur only a few tenths of an eV higher in energy relative to the antiferromagnetically-coupled ground state, a testament to much stronger metal-ligand orbital interactions for the heavier transition elements. This result provides a rare Paper Dalton Transactions measure of metal-ligand magnetic coupling for a 4d transition metal.…”

“…[6][7][8] The rarity of well-characterized, noninnocent 4d and 5d metal systems reflects in part the rarity of stable, paramagnetic complexes involving these elements (which in turn reflects their preference for low-spin states), robbing magnetic resonance methods such as paramagnetic NMR and EPR spectroscopy of the ability to characterize the phenomenon by probing molecular spin densities. [9][10][11][12][13][14][15][16] It is against this backdrop that we have chosen to reexamine paramagnetic molybdenum- 17 and tungsten- 18 dichlorido "Viking-helmet" corroles with density functional theory methods for possible signs of a noninnocent corrole (Scheme 1; see also Notes).…”

“…In recent years, metallocorroles have provided many examples of well-characterized noninnocent systems. [19][20][21][22] Key examples include MnCl, 23 FeCl, [9][10][11][12][13][14][15] FeNO, [24][25][26][27] Fe 2 (μ-O), 28 Copy 29 /DMSO 30 ( py = pyridine), Co-PPh 3 , 31 and Cu [32][33][34][35][36][37][38][39][40] corrole derivatives. It is worth noting that all these involve first-row transition metals.…”

Corroles and Hexaphyrins: Synthesis and Application in Cancer Photodynamic Therapy

“…The synthesis of iron(II) corrolate 59 has been described, as well as its reactivity towards molecular oxygen and organic electrophiles ( Scheme 23 ) [ 60 ]. The reaction of corrole 58 with stoichiometric quantities of KC8 in tetrahydrofuran afforded the iron(II) corrolate 59 , K(THF)2[Fe(TPC)].…”