ISSN:
0749-1581
Keywords:
1H NMR
;
2H NMR
;
Iron
;
Porphyrin
;
Isoporphyrin
;
Tetraphenylporphyrin
;
N-Phenyltetraphenylporphyrin
;
Aryl Grignard reagents
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Addition of aryl Grignard reagents to an iron(III) tetraphenylporphyrin π cation radical, [(TPP⋅)FeIIICl] (SbCl6), in dichloromethane solution at 202 K yields a mixture of σ-phenyl iron(IV) tetraphenylporphyrin, [(TPP)FeIV(Ph)] (SbCl6), and σ-phenyl iron(III) tetraphenylporphyrin, (TPP)FeIIICl. A σ-phenyliron(III) complex is also formed by nucleophilic addition to the tetraphenylporphyrin macrocycle accompanied by σ-phenyl axial coordination. The complexes formed were identified by 1H NMR spectroscopy. A new route for generating σ-aryl iron(IV) porphyrin species from the iron(III) porphyrin π cation radical was established. The characteristic 1H NMR pattern of the low-spin iron(III) porphyrin ring modified species reflects its Cs symmetry and includes four upfield-shifted pyrrole resonances (2.31, -10.40, 20.39 and -20.87 ppm, 202 K) accompanied by a set of σ-phenyl resonances (ortho, -188.4; p-H, -102.5; p-CH3 for σ-p-tolyl, 162.3 ppm). Analysis of the paramagnetic shifts of the σ-phenyl (σ-p-tolyl) ligand of the new species indicates a high π spin density consistent with the electronic structure of low-spin iron(III) and the contribution of a σ-delocalization mechanism via donation from a filled σ-phenyl orbital to an empty dz2; orbital. The formation of a low-spin σ-phenyliron(III) isoporphyrin or low-spin σ-phenyl N-arylporphyrin is considered. The meso substitution can be accounted for by a mechanism which emphasizes the radical nature of the reaction substrate and involves the formation of σ-transient forms.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260311311
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