770737-84-3Relevant academic research and scientific papers
Reactivity of iron(II) 5,10,15,20-tetraaryl-21-oxaporphyrin with arylmagnesium bromide: Formation of paramagnetic six-coordinate complexes with two axial aryl groups
Pawlicki, Milosz,Latos-Grazynski, Lechoslaw
, p. 5564 - 5571 (2008/10/09)
Coordination of σ-aryl carbanions by chloroiron(II) 5,20-ditolyl-10,15-diphenyl-21-oxaporphyrin (ODTDPP)FeIICl has been followed by 1H 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 (C 6H5)MgBr carried at 205 K yields a rare six-coordinate species which binds two σ-aryl ligands [(ODTDPP)FeII(C 6H5)2]-. Warming of the [(ODTDPP)FeII(C6H5)2] solution above 270 K results in the decomposition to mono-σ-phenyliron species (ODTDPP)FeIIC6H5). Controlled oxidation of [(ODTDPP)FeII(C6H5)2]- with Br2 affords (ODTDPP)FeII(C6H 5)Br, which demonstrates a typical 1H 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 1H 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 1H 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 β-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.
