Wydział Chemii

Miłosz Pawlicki

Lechosław Latos-Grażyński

2004

Inorganic Chemistry

43

5564-5571

10.1021/ic0495463

Naukowa

Angielski

Artykuł

Coordination of σ-aryl carbanions by chloroiron(II) 5,20-ditolyl-10,15-diphenyl-21-oxaporphyrin (ODTDPP)FeIICl has been followed by 1 H NMR spectroscopy. Addition of pentafluorophenyl Grignard reagent (C6F5)MgBr to the toluene solution of (ODTDPP)FeIICl in the absence of dioxygen at 205 K resulted in the formation of the high-spin (ODTDPP)- FeII(C6F5). The titration of (ODTDPP)FeIICl with a solution of (C6H5)MgBr carried at 205 K yields a rare six-coordinate species which binds two σ-aryl ligands [(ODTDPP)FeII(C6H5)2] -. Warming of the [(ODTDPP)FeII(C6H5)2] - solution above 270 K results in the decomposition to mono-σ-phenyliron species (ODTDPP)FeII(C6H5). Controlled oxidation of [(ODTDPP)FeII(C6H5)2] - with Br2 affords (ODTDPP)FeIII(C6H5)Br, which demonstrates a typical 1 H NMR pattern of low-spin σ-aryl iron(III) porphyrin. The considered oxidation mechanism involves the (ODTDPP)FeIII(C6H5)2 species, which is readily reduced to the iron(I) 21-oxaporphyrin, followed by oxidation with Br2 and replacement of one bromide anion by aryl substituent. The 1 H NMR spectra of paramagnetic iron complexes have been examined in detail. Functional group assignments have been made with the use of selective deuteration. The peculiar 1 H NMR spectral features of [(ODTDPP)FeII(p-CH3C6H4)2] - (σ-p-tolyl: ortho, 30.8; meta, 53.6; para-CH3, 42.1; furan: −16.0; â-H pyrrole: −27.5, −34.3, −41.8 ppm, at 205 K) are without a parallel to any iron(II) porphyrin or heteroporphyrin and indicate a profound alteration of the electronic structure of iron(II) porphyrin upon the coordination of two σ-aryls.

https://doi.org/10.1021/ic0495463

https://www.acs.org/content/acs/en.html