X-ray absorption spectroscopic studies of high-spin nonheme (alkylperoxo)iron(III) intermediates.
The reactions of iron(II) complexes [Fe(T(pt-Bu,i-Pr))(OH)] (1a, Tp(t-Bu,i-Pr) = hydrotris(3-tert-butyl-5-isopropyl-1-pyrazolyl)borate), [Fe(6-Me2BPMCN)(OTf)2] (1b, 6-Me2BPMCN = N,N'-bis((2-methylpyridin-6-yl)methyl)-N,N'-dimethyl-trans-1,2-diaminocyclohexane), and [Fe(L8Py2)(OTf)](OTf) (1c, L8Py2 = 1,5-bis(pyridin-2-ylmethyl)-1,5-diazacyclooctane) with tert-BuOOH give rise to high-spin FeIII-OOR complexes. X-ray absorption spectra (XAS) of these high-spin species show characteristic features, distinct from those of low-spin Fe-OOR complexes (Rohde, J.-U.; et al. J. Am. Chem. Soc. 2004, 126, 16750-16761). These include (1) an intense 1s --> 3d preedge feature, with an area around 20 units, (2) an edge energy, ranging from 7122 to 7126 eV, that is affected by the coordination environment, and (3) a 1.86-1.96 A Fe-OOR bond, compared to the 1.78 A Fe-OOR bond in low-spin complexes. These unique features likely arise from a flexible first coordination sphere in those complexes. The difference in Fe-OOR bond length may rationalize differences in reactivity between low-spin and high-spin FeIII-OOR species.
Shan
Xiaopeng
X
Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Rohde
Jan-Uwe
JU
Koehntop
Kevin D
KD
Zhou
Yuming
Y
Bukowski
Michael R
MR
Costas
Miquel
M
Fujisawa
Kiyoshi
K
Que
Lawrence
L
D005290:Ferric Compounds / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*; D014965:X-Rays
D005290:Ferric Compounds