Kinetics and mechanism of oxygen transfer in the reaction of p-cyano-N,N-dimethylaniline N-oxide with metalloporphyrin salts. 6. Oxygen atom transfer to and from the iron(III) C2cap porphyrin of Baldwin
| Autor: | T. C. Woon, P. N. Balasubramanian, F.-L. Lu, Thomas C. Bruice, C. M. Dicken |
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| Rok vydání: | 1987 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 109:3436-3443 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja00245a040 |
| Popis: | The decomposition of p-cyano-N,N-dimethylaniline N-oxide (NO) is catalyzed (CH/sub 2/Cl/sub 2/ solvent at 25 /sup 0/C) by the SbF/sub 6//sup -/ salt of the C/sub 2/-capped (meso-tetraphenylporphinato)iron(III) of Baldwin ((TPPC/sub 2/cap)Fe/sup III/SbF/sub 6/). Since neither NO nor the SbF/sub 6//sup -/ anion can fit under the cap, this result establishes that oxygen transfer from NO to the iron(III) center can occur without the intermediate iron(IV)-oxo porphyrin ..pi..-cation being hexacoordinated. The products of NO decomposition (p-cyano-N,N-dimethylaniline (DA) 68%, p-cyano-N-methylaniline (MA) 12%, p-cyanoaniline (A) 1%, N-formyl-p-cyano-N-methylaniline (FA) 6%, N,N'-dimethyl-N,N'-bis(p-cyanophenyl)hydrazine (H) 7%, and CH/sub 2/O 3%) account for 100% of the p-cyanodimethylaniline moiety of NO, but ca. 40% of the oxide oxygen of NO remains unaccounted for by product isolation. This is due to some loss of the catalyst and oxidation of the CH/sub 2/Cl/sub 2/ solvent during turnover. Oxidation of solvent results in gradual exchange of the SbF/sub 6//sup -/ axial ligand for Cl/sup -/. Product formation on reaction of NO with (TPPC/sub 2/cap)Fe/sup III/SbF/sub 6/ can be approximated by the first-order rate law. Since the observed first-order rate constants at a given (NO)/sub i/ are a linear function of the iron(III) porphyrin, the reaction is first order in this catalyst andmore » essentially so in NO. However, the finding that the initial rates are independent of (NO)/sub i/ establishes that the iron(III) porphyrin catalyst is saturated with NO on initiation of the reaction.« less |
| Databáze: | OpenAIRE |
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