REACTION OF CARBON-MONOXIDE WITH ALKYLIRON PORPHYRINS GENERATED FROM ALKYL-HALIDES AND ELECTROCHEMICALLY PRODUCED IRON(I) AND IRON(0) PORPHYRINS

Carbon monoxide inserts in iron-carbon bonds of σ-alkyl porphyrins generated from the reaction of alkyl halides with electrochemically produced low-valent iron porphyrins, with the exception of benzyl derivatives. In the case of σ-aryl complexes, the iron-carbon appears toostrong to allow CO insertion. In the case of methyl and other primary alkyls, CO insertion occurs at the Fe(III)-C rather than at the Fe(II)-C oxidation state. Insertion is then accompanied by partial homolysis of the σ-alkyl-Fe(III) complex favored by the binding of CO to the resulting iron(II)porphyrin. The latter reaction prevents the insertion of CO in the iron(III)-tert-butyl complex. However, CO then inserts in the Fe(II)-tert-butyl bond. The reaction mechanism is established and the characteristic rate constants are estimated on the basis of cyclic voltammetry, thin-layer spectroelectrochemistry, and preparative-scale electrolysis. © 1990, American Chemical Society. All rights reserved.