Crystal structure of bis(1-ethyl-1H-imidazole-κN 3)(5,10,15,20-tetraphenylporphyrinato-κ4 N)iron(II) tetrahydrofuran monosolvate

The title iron(II)–porphyrin complex possesses inversion symmetry with the metal atom located on a center of symmetry. The iron(II) atom is coordinated in a symmetric octahedral geometry by four pyrrole N atoms of the porphyrin ligand in the equatorial plane and two N atoms of 1-ethylimidazole ligands in the axial sites. The dihedral angle between the 1-ethylimidazole plane and the plane of the closest Fe—Np vector is 24.5(?)°.


Structural commentary
The asymmetric unit of the title compound ( Fig. 1), contains half of an Fe II porphyrin complex, with the iron(II) atom located on an inversion center, an 1-ethylimidazole ligand molecule, and half of a THF solvent molecule. The THF molecule is disordered over two positions; the site occupancy factors (SOFs) of the two disordered moieties being 0.35 and 0.15. The two 1-ethylimidazole ligands of [Fe II (TPP)(1-EtIm) 2 ] are mutually parallel, as required by the crystal symmetry. Additional quantitative information about the ISSN 2056-9890 structure is displayed in Fig. 2, which includes the displacement of each porphyrin core atom (in units of 0.01 Å ) from the 24-atom mean plane. The orientation of the 1-ethylimidazole ligand including the value of the dihedral angles is also given. As can be seen in Fig. 2, the porphyrin core of [Fe II (TPP)(1-EtIm) 2 ] is near-planar and the iron(II) atom is in the 24-atom plane. The displacements of every porphyrin core atom is less than 0.06 Å .  (Hu et al., 2016), which are typical values for six-coordinated low-spin (porphinato)iron(II) derivatives (Scheidt et al., 1981). The axial Fe-N Im bond length is 1.994 (2) Å . The average N p -Fe-N p angle is ideal at 90.00 (6) . The dihedral angle between the 1-ethylimidazole plane and the plane of the closest Fe-N p vector is 24.5 .

Supramolecular features
In the title compound, as shown in Fig. 3, the distance between the hydrogen atom H14B (C14) of the ethyl group of 1-EtIm and the pyrrole plane of the neighboring porphyrin is 2.66 Å , smaller than 2.9 Å , which is a limit suggested for the existence of a C-HÁ Á Á interaction (Takahashi et al., 2001). Details of this interaction are given in Table 1. The molecular packing is shown in Fig. 4.   The molecular structure of the title complex, with displacement ellipsoids drawn at the 50% probability level. The disordered THF molecule has been omitted for clarity, and unlabelled atoms are related to labelled atoms by the inversion symmetry code: (i) Àx, Ày + 1, Àz + 1. Table 1 Hydrogen-bond geometry (Å , ).

D-HÁ
The purple powder [Fe(TPP)] 2 O (15.9 mg, 0.018 mmol) was dried in vacuum for 1 h in a Schlenk tube. Benzene ($5 ml) was transferred into the Schlenk tube by cannula and ethanethiol (2 ml, 0.028 mol) was added via syringe. The mixture was stirred under argon at ambient temperature. After 36 h, the reduction was complete and the solvent was evaporated by pump. THF ($5 ml) was transferred into the Schlenk tube via a cannula, and 1-ethylimidazole (0.5 ml, 5.19 mmol) was added using a syringe. Hexanes were then allowed to diffuse slowly into the reaction solution. After several weeks purple block-shaped crystals of the title compound were obtained. A view along the a axis of the molecular packing of the title compound. H atoms have been omitted for clarity.

Figure 3
The C-HÁ Á Á interactions in the title compound. Dashed lines show the distances between H atoms of 1-ethylimidazole and the pyrrole core planes. Solvent (THF) molecules and other H atoms have been omitted for clarity.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The hydrogen atoms (H14A, H14B) attached to atom C14 of the 1-ethylimidazole ligand were located in a difference-Fourier map and refined freely. All other hydrogen atoms were placed in calculated positions (C-H = 0.95, 0.98 and 0.99 Å for aryl, methyl and methlyene H atoms, respectively) and refined using a riding model with U iso (H) = 1.5U eq (C) for methyl H atoms or U iso (H) = 1.2U eq (C) otherwise. The C-O, C-C, CÁ Á ÁC distances in the disordered THF molecule were constrained to 1.42 (1) Data collection: APEX2 (Bruker, 2014); cell refinement: SHELXL2014 (Sheldrick, 2015b); data reduction: SAINT-Plus (Bruker, 2014) and XPREP (Bruker, 2014); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: XP (Sheldrick, 2008) and Mercury (Macrae et al., 2008); software used to prepare material for publication: XCIF (Sheldrick, 2008) and enCIFer (Allen et al., 2004). Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (