Rohde Jan-Uwe, Betley Theodore A, Jackson Timothy A, Saouma Caroline T, Peters Jonas C, Que Lawrence
Department of Chemistry and Center for Metals in Biocatalysis, 207 Pleasant Street Southeast, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Inorg Chem. 2007 Jul 9;46(14):5720-6. doi: 10.1021/ic700818q. Epub 2007 Jun 15.
X-ray absorption spectroscopy has been used to characterize the novel nitridoiron(IV) units in two [PhBPR3]Fe(N) complexes (R=iPr and CyCH2) and obtain direct spectroscopic evidence for a very short Fe-N distance. The distance of 1.51-1.55 A reflects the presence of an FeN triple bond in accord with the observed FeN vibration observed for one of these species (nuFeN=1034 cm(-1)). This highly covalent bonding interaction results in the appearance of an unusually intense pre-edge peak, whose estimated area of 100(20) units is much larger than those of the related tetrahedral complexes with FeI-N2-FeI, FeII-NPh2, and FeIIINAd motifs, and those of recently described six-coordinate FeVN and FeVIN complexes. The observation that the FeIV-N distances of two [PhBPR3]Fe(N) complexes are shorter than the FeIV-O bond lengths of oxoiron(IV) complexes may be rationalized on the basis of the greater pi basicity of the nitrido ligand than the oxo ligand and a lower metal coordination number for the Fe(N) complex.
X射线吸收光谱已被用于表征两种[PhBPR3]Fe(N)配合物（R = iPr和CyCH2）中的新型氮合铁(IV)单元，并获得了Fe-N距离非常短的直接光谱证据。1.51 - 1.55 Å的距离反映了FeN三键的存在，这与其中一种物种观察到的FeN振动（νFeN = 1034 cm(-1)）一致。这种高度共价的键合相互作用导致出现一个异常强烈的前缘峰，其估计面积为100(20)个单位，远大于具有FeI-N2-FeI、FeII-NPh2和FeIIINAd基序的相关四面体配合物以及最近描述的六配位FeVN和FeVIN配合物的前缘峰面积。两种[PhBPR3]Fe(N)配合物的FeIV-N距离比氧合铁(IV)配合物的FeIV-O键长短，这一观察结果可以基于氮合配体比氧合配体具有更大的π碱性以及Fe(N)配合物较低的金属配位数来解释。
