Iron-carbon dioxide complex, coordination

Carbon dioxide has been reduced to methanol with the Everitt s salt (ES)-mediated electrode in the presence of l,2-dihydroxybenzene-3,5-disul-phonato(iron) ferrate(III) complex (Scheme 103) [408, 409]. The reduction proceeds as follows a weak coordination bond is first formed between the central metal of ES and ethanol, then the subsequent insertion of CO2 onto... 

Structure 5.17. Tetraphenylporphyrin Iron(III) chloride, with basket-handle of the picket-fence type with secondary amide groups in close vicinity to the porphyrin ring. Reprinted from Structure 16 J. Costamagna, G. Ferraudi, J. Canales and J. Vargas, Carbon dioxide activation by aza-macrocychc complexes, Coordination Chemistry Reviews 148 (1996) 221-248. Copyright 1996, with permission of Elsevier. 

Iron(O) tetraphenylporphyrin is also a catalyst of the electrochemical carbon dioxide reduction to carbon monoxide in DMF electrolytes [29-31]. Under CO, the catalyst is, however, rapidly destroyed by either carboxylation or hydrogenation of the porphyrin ring. The mechanism proceeds through coordination of CO2 to Fe(0). At low temperature (-40°C), a second CO2 molecule adds to the first-coordinated one in an acid-base reaction fashion. This is followed by the cleavage of a C—O bond of the first-coordinated CO2 molecule and concomitant formation of the Fe(II)CO complex and a carbonate anion. After reduction of the Fe(ll)CO complex by the Fe(0) complex, CO is... 

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