415701-46-1Relevant articles and documents
Ligand dependence of binding to three-coordinate Fe(11) complexes
Chiang, Karen P.,Barrett, Pamela M.,Ding, Feizhi,Smith, Jeremy M.,Kingsley, Savariraj,Brennessel, William W.,Clark, Meghan M.,Lachicotte, Rene J.,Holland, Patrick L.
, p. 5106 - 5116 (2009/10/23)
A series of three- and four-coordinate iron(11) complexes with nitrogen, chlorine, oxygen, and sulfur ligands is presented. The electronic variation is explored by measuring the association constant of the neutral ligands and the reduction potential of the iron(11) complexes. Varying the neutral ligand gives large changes in Keq, which decrease in the order CNtBu > pyridine >2-picoline > DMF > MeCN > THF > PPh3. These differences can be attributed to a mixture of steric effects and electronic effects (both σ-donation and π-backbonding). The binding constants and the reduction potentials are surprisingly insensitive to changes in an anionic spectator ligand. This suggests that three-coordinate iron(11) complexes may have similar binding trends as proposed three-coordinate iron(11) intermediates in the FeMoco of nitrogenase, even though the anionic spectator ligands in the synthetic complexes differ from the sulfides in the FeMoco.
Quantitative geometric descriptions of the belt iron atoms of the iron-molybdenum cofactor of nitrogenase and synthetic iron(II) model complexes
Vela, Javier,Cirera, Jordi,Smith, Jeremy M.,Lachicotte, Rene J.,Flaschenriem, Christine J.,Alvarez, Santiago,Holland, Patrick L.
, p. 60 - 71 (2008/10/09)
Six of the seven iron atoms in the iron-molybdenum cofactor of nitrogenase display an unusual geometry, which is distorted from the tetrahedral geometry that is most common in iron-sulfur clusters. This distortion pulls the iron along one C3 axis of the tetrahedron toward a trigonal pyramid. The trigonal pyramidal coordination geometry is rare in four-coordinate transition metal complexes. In order to document this geometry in a systematic fashion in iron(II) chemistry, we have synthesized a range of four-coordinate iron(II) complexes that vary from tetrahedral to trigonal pyramidal. Continuous shape measures are used for a quantitative comparison of the stereochemistry of the Fe atoms in the iron-molybdenum cofactor with those of the presently and previously reported model complexes, as well as with those in polynuclear iron-sulfur compounds. This understanding of the iron coordination geometry is expected to assist in the design of synthetic analogues for intermediates in the nitrogenase catalytic cycle.
Three-coordinate, 12-electron organometallic complexes of iron(II) supported by a bulky β-diketiminate ligand: Synthesis and insertion of CO to give square-pyramidal complexes
Smith, Jeremy M.,Lachicotte, Rene J.,Holland, Patrick L.
, p. 4808 - 4814 (2008/10/08)
The preparation of a series of three-coordinate, 12-electron organometallic complexes of iron(II) supported by a bulky β-diketiminate ligand is described. The thermally stable complexes LFeR (R = Et, CH2tBu, iPr) are three-coordinate in both the solid state (single crystal X-ray diffraction) and solution. They react rapidly with CO to form the diamagnetic complexes LFe(CO)2(COR), which have an unusual square-pyramidal geometry. Spectroscopic and crystallographic studies show that the acyl group is in the axial position. As a result, there are two orientations of the acyl group about the Fe-C bond, and the isomeric ratio is dependent on the size of R. The two isomers are in equilibrium in solution at room temperature.
