(Cryptand-222)potassium(+) (hydrogensulfido)[5,10,15,20-tetra­kis(2-pival­amido­phen­yl)porphyrinato]ferrate(II)

Mondher Dhifet; Mohamed Salah Belkhiria; Jean-Claude Daran; Habib Nasri

doi:10.1107/S1600536809028104

. 2009 Jul 22;65(Pt 8):m967–m968. doi: 10.1107/S1600536809028104

(Cryptand-222)potassium(+) (hydrogensulfido)[5,10,15,20-tetrakis(2-pivalamidophenyl)porphyrinato]ferrate(II)

Mondher Dhifet ^a, Mohamed Salah Belkhiria ^a, Jean-Claude Daran ^b, Habib Nasri ^a,^*

PMCID: PMC2977240 PMID: 21583412

Abstract

As part of a systematic investigation for a number of Fe^II porphyrin complexes used as biomimetic models for cytochrome P450, crystals of the title compound, [K(C₁₈H₃₆N₂O₆)][Fe^II(C₆₄H₆₄N₈O₄)(HS)], were prepared. The compound exhibits a non-planar conformation with major ruffling and saddling distortions. The average equatorial iron–pyrrole N atom [Fe—N_p = 2.102 (2) Å] bond length and the distance between the Fe^II atom and the 24-atom core of the porphyrin ring (Fe—P_C= 0.558 Å) are typical for high-spin iron(II) pentacoordinate porphyrinates. One of the tert-butyl groups in the structure is disordered over two sets with occupancies of 0.84 and 0.16.

Related literature

For general background to iron(II) porphyrin species and their applications, see: Simonneux & Le Maux (2000 ▶). For a description of the Cambridge Structural Database, see: Allen (2002 ▶). For the synthesis of iron(II) picket fence derivatives, see: Collman et al. (1975 ▶); Nasri et al. (1987 ▶); Hachem et al. (2009 ▶). For related structures, see: English et al. (1984 ▶); Nasri et al. (2000 ▶). For further details of geometric distortions in related compounds, see: Scheidt & Reed (1981 ▶); Scheidt (2000 ▶); Hu et al. (2005 ▶); Jentzen et al. (1997 ▶). For comparitive bond lengths, see: Allen et al. (1987 ▶). For the treatment of disordered solvent of crystallization, see: Spek (2009 ▶); Stähler et al. (2001 ▶); Cox et al. (2003 ▶); Mohamed et al. (2003 ▶); Athimoolam et al. (2005 ▶).

Experimental

Crystal data

[K(C₁₈H₃₆N₂O₆)][Fe(C₆₄H₆₄N₈O₄)(HS)]
M _r = 1513.74
Monoclinic,
a = 17.9327 (7) Å
b = 21.5340 (7) Å
c = 22.7670 (9) Å
β = 100.611 (2)°
V = 8641.4 (6) Å³
Z = 4
Mo Kα radiation
μ = 0.31 mm⁻¹
T = 180 K
0.25 × 0.24 × 0.21 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2007 ▶) T _min = 0.842, T _max = 0.937
144342 measured reflections
12322 independent reflections
10135 reflections with I > 2σ(I)
R _int = 0.048
θ_max = 23.2°

Refinement

R[F ² > 2σ(F ²)] = 0.046
wR(F ²) = 0.128
S = 1.05
12322 reflections
965 parameters
9 restraints
H-atom parameters constrained
Δρ_max = 0.58 e Å⁻³
Δρ_min = −0.45 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SIR2004 (Burla et al., 2005 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEPIII (Burnett & Johnson, 1996 ▶) and ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809028104/bg2280sup1.cif

e-65-0m967-sup1.cif^{(50.8KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809028104/bg2280Isup2.hkl

e-65-0m967-Isup2.hkl^{(590.3KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

The authors gratefully acknowledge financial support from the Ministry of Higher Education, Scientific Research and Technology of Tunisia.

supplementary crystallographic information

Comment

A large number of iron-thiolate porphyrin complexes have been investigated in order to get more insight into the nature of the electronic and steriochemical properties of cytochromes P450 (Simonneux & Le Maux, 2000). In the Cambridge Structural Database (CSD, Version 5.30 of November 2008; Allen, 2002) there are only three structures of iron(II)-thiolate porphyrinates but no structure of hydrosulfido (SH^-) iron(II) porphyrinate derivative is reported up to date. We report here the molecular structure of the iron(II) picket fence porphyrin (TpivPP) hydrosulfido species. In the structure of (I), the Fe²⁺ cation is coordinated to the sulfur atom of the SH^- axial ligand from the pocket side of the TpivPP porphyrin (Fig. 1). The porphinato core undergoes a significant radial expansion in order to accommodate the high-spin Fe²⁺ cation. This is illustrated by the long Fe—N_p and Fe—P_C distances shown by these iron(II) high-spin [Fe^II(Porph)(X)]^- complexes (X = anionic monodentate ligand). The average equatorial Fe—N_p distance in (I) [2.102 (2) Å], which is longer than the corresponding Fe³⁺ species [Fe^III(TAP)(SH)] (English et al., 1984) (TAP = tetrakis(p-methoxyphenyl)porphyrinate(2-) [2.015 (2) Å], falls within the range found for five-coordinate high-spin iron(II) porphyrins [2.072- 2.116 Å] (Scheidt & Reed, 1981; Scheidt, 2000; Hu et al., 2005). This is a stereochemical proof that compound (I) is high-spin (S = 2). The Fe—P~C distance [0.7578 Å] is quite longer than those of iron(II) high-spin five-coordinate porphyrines [0.50 – 0.64 Å]. For our model, the axial Fe—S(SH) bond length [2.312 (1) Å] is slightly shorter than those of the three iron(II)-thiolate porphyrinates cited in the literature [2.325 – 2.367 Å]. This distance is longer than the one of the [Fe^III(TAP)(SH)] derivative [2.298 (3) Å]. It is noteworthy that Fe—SH distance for compound (I) is shorter than the Fe—S(thiole) bond length found for iron(II) thiole porphyrin species, i.e. for the ion complex [Fe^II(TpivPP)(NO₂)(PMS)]^- (Nasri et al., 2000) where PMS = pentamethylene sulfide) the Fe—S(PMS) distance is 2.380 (4) Å. The structural decomposition method [NSD] (Jentzen et al., 1997) indicates an important ruffling [41%], a quite high saddling [21%] and a moderate doming [14%] of the porphinato core. The negative charge of the [Fe^II(TpivPP)(SH)]^- anion is balanced by a [K(2,2,2-crypt)]⁺ counterion. The average K—O(2,2,2-crypt) and K—N(2,2,2-crypt) distances [2.827 (2) Å and 3.035 (3) Å respectively] are in agreement with the literature values (Allen et al., 1987). There are no intermolecular or intermolecular hydrogen bonds in the structure of (I). The packing diagram for (I) (Fig.2) is simple. There is no evidence for intermolecular π -π bonding between the faces of the porphyrin cores in compound (I). The absence of the π -π interactions results mainly in the steric restrictions requirements of the pivalamide groups that determine the packing environment.

Experimental

The reaction sequence leading to the formation of compound (I) is not full understood at present. When a chlorobenzene solution of [Fe^II(TpivPP)] (Hachem et al., 2009), made in situ, is mixed under argon with excess of cryptand-222 and potassium thioacetate (C₂H₃OSK) a red-greenish solution was formed. Crystals of (I) were grown by diffusion of hexanes through the chlorobenzene solution.