Synthesis, crystal structure and characterizations of di-μ-cyanido-1:2κ2 N:C;2:3κ2 C:N-bis-(4,7,13,16,21,24-hexa-oxa-1,10-di-aza-bicyclo-[8.8.8]hexacosa-ne)-1κ8 N 1,N 10,O 4,O 7,O 13,O 16,O 21,O 24;3κ8 N 1,N 10,O 4,O 7,O 13,O 16,O 21,O 24-[5,10,15,20-tetra-kis-(4-chloro-phen-yl)porphyrinato-2κ4 N]-2-iron(II)-1,3-dipotassium(I) tetra-hydro-furan disolvate with an unknown solvent.

Tingting Huang,Jianping Zhao,Haimang Wang

doi:10.1107/s2056989019014841

Abstract

The title compound, [Fe(C44H24N8Cl4)(CN)2][K2(C18H36N2O6)2]·2C4H8O was synthesized and characterized by single-crystal X-ray diffraction as well as FTIR and UV-vis spectroscopy. The central FeII ion is coordinated by four pyrrole N atoms of the porphyrin core and two C atoms of the cyano groups in a slightly distorted octa-hedral coordination environment. The complex mol-ecule crystallizes with two tetra-hydro-furan solvent mol-ecules, one of which was refined as disordered over two sets of sites with refined occupancies of 0.619 (5) and 0.381 (5). It has a distorted porphyrin core with mean absolute core-atom displacements Ca, Cb, Cm and Cav of 0.32 (3), 0.22 (3), 0.56 (2) and 0.37 (14) Å, respectively. The axial Fe-Ccyano bond lengths are 1.991 (2) and 1.988 (2) Å. The average Fe-Np (Np is a porphyrin N atom) bond length is 1.964 (10) Å. One of the O atoms and several C atoms of the 222 moiety [222 = 4,7,13,16,21,24-hexa-oxa-1,10-di-aza-bicyclo-[8.8.8]hexa-cosa-ne] were refined as disordered over two sets of sites with occupancy ratios of 0.739 (6):0.261 (6) and 0.832 (4):0.168 (4). Additional solvent mol-ecules were found to be highly disordered and their contribution to the scattering was removed using the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18], which indicated a solvent cavity of volume 372 Å3 containing approximately 83 electrons. These solvent mol-ecules are not considered in the given chemical formula and other crystal data.

Highlights

The cyanide ion, CNÀ, a well-known acute chemical poison, acts by inhibiting the enzyme cytochrome c oxidase, which catalyses the conversion of O2 to H2O along with the captured biological energy necessary to sustain life (Li et al, 2015)
Since the reaction of cyanide with ferrohemes has been relatively little studied owing to the low stability of the complexes even at alkaline pH values
In the title compound (Fig. 1), the asymmetric unit contains one six-coordinated iron(II) porphyrin in which the carbon atoms C27 and C28 of the cyanide ligands ligate to the central FeII ion, two cyano-bound [K(222)]+ ligands and two tetrahydrofuran solvent molecules

Summary

Chemical context

The cyanide ion, CNÀ, a well-known acute chemical poison, acts by inhibiting the enzyme cytochrome c oxidase, which catalyses the conversion of O2 to H2O along with the captured biological energy necessary to sustain life (Li et al, 2015). It is often used as a ligand in ferric heme proteins in order to prepare low-spin (S = 1/2) ferric derivatives. The crystal structure of an iron(II) porphyrin complex, [K(222)]2[FeII(TpClPP)(CN)2]Á2THF is reported where TpClPP is 5,10,15,20-tetrakis(p-chlorophenyl) porphyrinato4N and 222 is 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane and is used to stabilize the K+ cation. Distances between the carbon atoms (hydrogen atoms) of [K(222)]+ and the close pyrrole ring centroids are shown in Fig. 4, and the geometrical parameters are listed in Table 1; all are in the range of C—HÁ Á Á interactions (Takahashi et al, 2001)

Structural commentary

Supramolecular features

FTIR spectroscopy

General procedure

Synthesis of the title compound

Refinement