Iron complexes coordination geometries

Other paramagnetic bis(amidinate) iron(II) complexes of the type [But(NR)2]2Fe (R = Cy, Pr ) have been prepared analogously from the lithium amidinate salts and FeCl2- The coordination geometry around Fe is distorted tetrahedral (Scheme 137). 

A mononuclear diastereopure high-spin Fe alkylperoxo complex with a pen-tadentate N,N,N,0,0-ligand 33 (Scheme 17) was reported by Klein Gebbink and coworkers [109, 110]. The complex is characterized by unusual seven-coordinate geometry. However, in the oxidation of ethylbenzene the iron complex with 33 and TBHP yielded with large excess of substrate only low TON s (4) and low ee (6.5%) of 1-phenylethanol. 

Power and coworkers prepared the iron(V) bis-imide complex 3,5-Pr2 Ar Fe[N (1-Ad)]2l [42]. This complex has been characterized by X-ray crystallography with the iron in planar three-coordinate geometry. The Fe-N bond distances are 1.642(2) and 1.619(2)A. Magnetic studies of 3,5-Pr2 Ar Fe[N(l-Ad)]2 reveals that this complex has a low-spin cP configuration with S = jl ground state. This compound is notable as it is a stable Fe(V) imide being well characterized. 

The geometry of the ferrous iron is trigonal bipyramidal. Thus, this structure confirms the tendency of iron complexes to coordination numbers higher than four. The two N-donors and one of the carboxylates of 5 occupy the equatorial positions. In good agreement... 

The characterization, redox properties, and pulse radiolysis study of manganese(III) complexes of type [MnLCy (where L = cyclam, meso-, and rac-5,7,7,12,14,14-hexamethylcyclam (tet a and tet b, respectively)) have been reported." An X-ray crystal structure of the meso-5,l,l, 2, A, A-hexamethyl-l,4,8,ll-tetraazacyclotetradecane complex shows that the coordination geometry of the tet a complex is close to octahedral with the macrocycle coordinated equatorially and the chlorides occupying irons axial sites. 

The most elegant example which demonstrates this aspect of proton transfer equilibrium of heme proteins is the study reported on six coordinated aqua (pyridine) iron(III) porphyrin complexes encapsulated in aqueous micelles [27]. The ferric ion in these complexes is axially co-ordinated to a water and a pyridine molecule, thus having a coordination geometry similar to that of the heme in metmyoglobin. The pH dependence of the absorption spectra of the... 

Locating minima is not always straightforward since a reaction surface is usually complex, and a geometry optimization calculation will only locate minima close to the starting point. It is usually not feasible to systematically explore all possible conformers, so chemical intuition and corroborative evidence from experiment play important roles. A nice example is the identification of the coordination geometry of oxo-iron(IV) intermediate in TauD (22). As mentioned above, during optimization of enzyme active sites, key atoms are sometimes fixed to mimic the constraints that the protein environment exerts on the active site (20). 

The structure of the monomeric low-spin (2.46 BM, room temp.) Fe(f-BuSXant)3 complex has been determined (406) (Table XIX). The coordination geometry of the iron atom is a distorted octahedron of sulfur atoms contributed by the three chelating thioxanthate ligands. The structure of the low-spin (/ieff = 2.7 BM) Fe(EtXant)3 complex has been found to contain a distorted octahedral FeS6 core (340). 

The structure of the l,2,3,6-f/4-OFCOT complex 64 is shown in Fig. 6 (140). The coordination geometry around iron can be considered as octahedral, with the allylic portion of the OFCOT ligand and the Fe—C a bond occupying three facial sites. The formal oxidation of the metal center is reflected in the higher values of the CO stretching frequencies (vco = 2105, 2060 cm-1) for complex 64 compared to those for the l-4-r/4-COT complex 63 (vco = 2051, 1992, 1978 cm-1) (139). 

Draw the structure of the iron oxalate complex [Fe(C204)3]3-. Describe the coordination geometry, and identify any chelate rings. What are the coordination number and the oxidation number of the iron ... 

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