Low-Spin Bis(2-methylimidazole)(octaethylporphyrinato)iron(III) Chloride (perp-[Fe(OEP)(2-MeHIm)₂]Cl):  A Consequence of Hydrogen Bonding?

Abstract

The synthesis and characterization of low-spin bis(2-methylimidazole)(octaethylporphyrinato)iron (III) chloride (perp-[Fe(OEP)(2-MeHIm) 2 ]Cl) is reported. The structure shows that the cation is a low-spin species with two imidazole ligands having a relative perpendicular orientation. The porphyrin core is very ruffled, which leads to shortened equatorial bonds of 1.974 (4)

Crystal structure of bis(2-methyl-1H-imidazole-κN3)(meso-tetra-p-tolylporphyrinato-κ4N)iron(III) perchlorate tetrahydrofuran sesquisolvate

“…3, the perchlorate ion bridges two adjacent porphyrin molecules through hydrogen bonding with imidazole ligands, which can be formulated as N8-H8AÁ Á ÁO2-ClO 2 -O3Á Á ÁH6A-N6, forming a chain parallel to [110]. The hydrogen-bonding distances, 2.942 (3) (O3Á Á ÁN6) and 2.949 (3) Å (O2Á Á ÁN8), are consistent with the reported values 2.92 or 3.08 Å (Scheidt et al, 1987;Hu et al, 2006), and fall in the range 2.70-3.30 Å reported for intermolecular NÁ Á ÁO interactions (Bertolasi et al, 1995). It is noteworthy that one of the tetrahydrofuran molecules, which is disordered about an inversion center, Partial packing diagram of the title compound showing the formation of a chain through hydrogen bonding between the perchlorate ion and two imidazole ligands.…”

“…The mean absolute core atom displacements of C a , C b , C m , and C av are 0.25 (5), 0.17 (12), 0.432 (16) and 0.25 (13) Å , respectively. The mean Fe-N p (N p is a porphyrin N atom) bond length is 1.975 (9) Å , similar to 1.974 (4) Å in (perp-[Fe(OEP)-(2-MeHIm) 2 ]Cl) (Hu et al, 2006) and 1.970 (4) Å in [Fe(TPP)(2-MeHIm) 2 ]ClO 4 (Scheidt et al, 1987). These values are slightly shorter than 1.990 Å , which is typically observed for a low-spin iron(III) porphyrin complex (Scheidt & Reed, 1981).…”

“…The first ferric porphyrin crystal structure with two sterically hindered axial ligands is [Fe(OEP)(2-MeHIm) 2 ]ClO 4 , which was reported by Geiger and co-workers (Geiger et al, 1984). Subsequently, some other analogues have been reported, [Fe(TPP)(2-MeHIm) 2 ]ClO 4 (Scheidt et al, 1987), [Fe(TMP)(1,2-Me 2 Im) 2 ]ClO 4 (Munro et al, 1995), [Fe(OETPP)(2-MeHIm) 2 ]Á(0.33SbF 6-, 0.67Cl À ) (Ogura et al, 2001), [Fe(OMTPP)(2-MeHIm) 2 ]ClÁ3CD 2 Cl 2 (Yatsunyk et al, 2003), [Fe(OMTPP)(2-MeHIm) 2 ]ClÁ2CDCl 3 (Yatsunyk et al, 2003), perp-[Fe(OEP)(2-MeHIm) 2 ]Cl (Hu et al, 2006) (OEP, octaethylporphirin; TPP, tetraphenylporphphyrin; TMP, tetramesitylporphyrin; OETPP, octaethyltetraphenylporphyrin; OMTPP, octamethyltetraphenylporphyrin; 2-MeHIm, 2-methylimidazole; 1,2-Me 2 Im, 1,2-dimethylimidazole). Herein, we report the structural properties of the iron(III) porphyrin complex [Fe(TTP)(2-MeHIm) 2 ]-(ClO 4 )Á1.5THF where the metal is likewise octahedrally coordinated.…”

Synthesis and characterization of a modified “picket fence” porphyrin complex – stronger π bonding interactions between Fe(ii) and axial ligands

“…The data were fit to four overlapped Lorentzian lines for each temperature. 2,56 Table 3 gives the Mössbauer data of all known, six-coordinate low-spin species of [Fe(II)(Porph)(L) 2 ], also given are the relative ligand orientations and porphyrin core conformations. 6), the major component is 91% occupied.…”

Organometallic complexes as anion hosts

“…One could expect that these differences in bond lengths should be more pronounced for an anionic guest than for acetone. However, the differences between Re-N bond lengths in [Re(CO) 3 31 and hence to display shorter M-N lengths. 32 The fact that (although the difference is very small) the contrary is found suggests that our hypothesis of a loss of Re-N bonding character upon guest binding due to unfavorable N-Re-N angle opening may be correct.…”