Wydział Chemii

R. Koerner

Lechosław Latos-Grażyński

Alan L. Balch

1998

Journal of the American Chemical Society

120

9246-9255

10.1021/ja980558v

Naukowa

Angielski

Artykuł

Studies of the reaction of 5-oxaporphyrin iron complexes (verdohemes) with methoxide ion have been undertaken to provide models for the initial step in hydrolysis of verdohemes. Treatment of both low-spin [(py)₂Fe^II(OEOP)]Cl and high-spin {ClFe^II(OEOP)} (OEOP is the monoanion of octaethyl-5-oxaporphyrin) with methoxide ion in either pyridine or methanol solution is shown to cause ring opening and addition of methoxide to one end of the tetrapyrrole. Black {Fe^II(OEBOMe)}₂ has been isolated in crystalline form from the reaction of {ClFe^II(OEOP)} with methoxide in methanol and studied by single-crystal X-ray diffraction. The molecule has a centrosymmetric dimeric structure composed of two helical Fe(OEBOMe) units with FeN₄ coordination which are connected by a pair of Fe−O bonds. Each iron ion has approximately trigonal bipyramidal geometry. Evidence is presented which suggests that {Fe^II(OEBOMe)}₂ dissolves in dichloromethane in the presence of methanol or pyridine to form high-spin {(MeOH)_nFe^II(OEBOMe)} or {(py)_nFe^II(OEBOMe)} (n = 1 or 2) through rupture of the Fe−O bonds in the dimer. The electronic absorption spectra of these open chain complexes show characteristic low-energy features at ca. 720 and 810 nm. The ¹H NMR spectrum of {Fe^II(OEBOMe)}₂ at 23 °C shows a characteristic upfield methoxy resonance, 16 methylene resonances in the 47 to 5 ppm region, and meso resonances in the 51 to 29 ppm region. The temperature dependence of these spectra shows marked deviations from the Curie law, which are consistent with a dimeric structure.

Alcohols, Iron, Oxidation, Pyridines, pyrroles

https://doi.org/10.1021/ja980558v

https://www.acs.org/content/acs/en.html