Related Experiment Video
Updated: May 28, 2026
Preparation of 6-aminocyclohepta-2,4-dien-1-one Derivatives via Tricarbonyl(tropone)iron
Published on: August 12, 2019
Ligand adducts of bis(acetylacetonato)iron(II): a 1H NMR study
Zhigang Xue1, Jean-Claude Daran, Yohan Champouret
1Laboratoire de Chimie de Coordination, Université de Toulouse, UPS, INP, 205, route de Narbonne, F-31077 Toulouse, France.
Abstract:
We report here a thorough (1)H NMR study of Fe(acac)(2) solutions in a wide variety of noncoordinating and coordinating solvents, as well as the interaction of this complex with Et(3)N, pyridine, PMe(2)Ph, and R(2)PCH(2)CH(2)PR(2) [R = Ph (dppe), Et (depe)] in C(6)D(6). The study reveals that Fe(acac)(2) is readily transformed into Fe(acac)(3) in solution under aerobic conditions and that the commercial compound is usually contaminated by significant amounts of Fe(acac)(3). The (1)H NMR resonances of Fe(acac)(2) are rather solvent-dependent and quite different than those reported in the literature. The compound is unstable in CDCl(3) and stable in CD(2)Cl(2), C(6)D(6), CD(3)CN, acetone-d(6), DMSO-d(6), THF-d(8), and CD(3)OD. The addition of the above-mentioned ligands (L) reveals only one paramagnetically shifted band for each type of acac and L proton, the position of which varies with the L/Fe ratio, consistent with rapid ligand exchange equilibria on the NMR time scale. A fit of the NMR data at a high L/Fe ratio allows the calculation of the expected resonances for all protons in the Fe(acac)(2)L(2) molecules. The system with the bidentate depe ligand shows evidence for a slow ligand exchange at low depe/Fe ratios, proposed to involve a species with the cis-chelated mononuclear Fe(acac)(2)(depe) structure, whereas the fast exchange at a higher ratio is proposed to involved a trans-Fe(acac)(2)(κ(1)-depe)(2) complex. Complex Fe(acac)(2)(dppe) cannot be investigated in solution because of low solubility in a noncoordinating solvent and because of the poor dppe competition for binding in coordinating solvents. The compound was crystallized, and its X-ray structure reveals a 1-dimensional polymeric structure with dppe-bridged Fe centers having the trans-octahedral Fe(acac)(2)(κ(1)-dppe)(2) coordination environment.
Related Concept Videos
02:51Metal-Ligand Bonds
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
00:43Complexometric Titration: Ligands
02:42Valence Bond Theory
03:02Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
01:19Complexation Equilibria: The Chelate Effect
02:34Structural Isomerism
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...