Iron(tetraphenylporphyrinato) chloride explained

Iron(tetraporphyrinato) chloride is the coordination complex with the formula Fe(TPP)Cl where TPP is the dianion [C₄₄H₂₈N₄]^2-. The compound forms blue microcrystals that dissolve in chlorinated solvent to give brown solutions. In terms of structure, the complex is five-coordinate with idealized C_4v point group symmetry.^[1] It is one of more common transition metal porphyrin complexes.

Synthesis and reactions

Fe(TPP)Cl is prepared by the reaction of tetraphenylporphyrin (H₂TPP) and ferrous chloride in the presence of air:

H₂TPP + FeCl₂ + 1/4 O₂ → Fe(TPP)Cl + HCl + 1/2 H₂O

The chloride can be replaced with other halides and pseudohalides. Base gives the "mu-oxo dimer":

2 Fe(TPP)Cl + 2 NaOH → [Fe(TPP)]₂O + 2 NaCl + H₂O

Most relevant to catalysis, the complex is easily reduced to give ferrous derivatives (L = pyridine, imidazole):

Fe(TPP)Cl + e- + 2 L → Fe(TPP)L₂ + Cl⁻

The complex is widely studied as a catalyst.^{[2] [3]}

References

1. 10.1021/ic5015835. Intermolecular Interactions in Solid-State Metalloporphyrins and Their Impacts on Crystal and Molecular Structures. 2014. Hunter. Seth C.. Smith. Brenda A.. Hoffmann. Christina M.. Wang. Xiaoping. Chen. Yu-Sheng. McIntyre. Garry J.. Xue. Zi-Ling. Inorganic Chemistry. 53. 21. 11552–11562. 25338536.
2. Book: 10.1002/047084289X.rn01388. Iron(III)meso-Tetraphenylporphine Chloride. Encyclopedia of Reagents for Organic Synthesis. 2012. Cui. Xin. Zhang. X. Peter. 978-0471936237.
3. 10.1021/jacs.9b02640. Mechanism of Catalytic O2 Reduction by Iron Tetraphenylporphyrin. 2019. Pegis. M. L.. Martin. D. J.. Wise. C. F.. Brezny. A. C.. Johnson. S. I.. Johnson. L. E.. Kumar. N.. Raugei. S.. Mayer. J. M.. Journal of the American Chemical Society. 141. 20. 8315–8326. 31042028. 6684231.