Verdoheme reactivity. Remarkable paramagnetically shifted H-1 NMR spectra of intermediates from the addition of hydroxide or methoxide with Fe-II andFe-III verdohemes

Studies of the reaction of 5-oxaporphyrin iron complexes (verdohemes) with methoxide ion or hydroxide ion have been undertaken to understand the initi al step of ring opening of verdohemes. High-spin {ClFeIII(OEOP)} undergoes a complex series of reactions upon treatment with hydroxide ion in chlorofo rm, and similar species are also detected in dichloromethane, acetonitrile, and dimethyl sulfoxide. Three distinct paramagnetic intermediates have bee n identified by H-1 NMR spectroscopy. These reactive species are formed by addition of hydroxide to the macrocycle and to the iron as an axial ligand. Treatment of low-spin [(py)(2)Fe-II(OEOP)]Cl (OEOP is the monoanion of oct acthyl-5-oxaporphyrin) with excess methoxide ion in pyridine solution produ ces {(py)(n)Fe-II(OEBOMe)} (n = 1 or 2) ((OEBOMe), dianion of octaethylmeth oxybiliverdin), whose H-1 NMR spectrum undergoes marked alteration upon add ition of further ammounts of methoxide ion. An identical H-1 NMR spectrum, which is characterized by methylene resonances with both upfield and downfi eld paramagnetic shifts, is formed upon treatment of {Fe-II(OEBOMe)}(2) wit h methoxide in pyridine solution and results from the formation of [(MeO)Fe -II(OEBOMe)](-).