Distorted square-pyramidal geometry

Macrocycles attached to redox responsive groups such as ferrocene (78) can give selective transition metal ion receptors. The X-ray structure reveals a five-coordinate zinc with distorted square-pyramidal geometry bound to the four macrocycle nitrogens and an iodide. In the solid state the two ferrocenyl groups are positioned on the same side of the ligand with distances to the metal center of 5.347(7) and 6.120(8) A and these distances can be related to the redox behavior.689... 

Methyl pyruvate thiosemicarbazone in the presence of zinc chloride or acetate resulted in the formation of complexes with the ligand hydrolyzed or transesterified. The complexes with pyruvate thiosemicarbazone, ZnL2, or ethyl pyruvate thiosemicarbazone, ZnLCl2 were structurally characterized by single-crystal X-ray crystallography showing respectively a distorted octahedral and distorted square pyramidal geometry.874... 

Pentacoordinated Pc complexes with planar macrocycle are very scarce. Very recently, Galezowski and Kubicki [25] reported a o-bonded ComPc(CH3CH2) (2) with an alkyl group as axial ligand. Investigation of its crystal structure revealed that the solid consists of centrosymmetric face-to-face dimers. The cobalt atom in 2 is pentacoordinated and has a distorted square pyramidal geometry. The cobalt atom... 

Nearly 50 crystal structure determinations of examples of 5 and 6 have now been determined and reveal that the geometry at the five-coordinate metal centres can be anywhere between square-pyramidal and trigonal bipyramidal (CSD search April 2008). For example, in [2,6-(ArN=CMe)2C5H3N]FeCl2 (5 Ar = 2,6-i-Pr2C6H3) a distorted square-pyramidal geometry at the metal is exhibited with the arylimino groups almost perpendicular to the plane of the bis(imino)pyridine backbone (Fig. 5) [5, 6], The overall result is that the metal centre is protected both above and below... 

Partial substitution of halides on bismuth predictably gives alkoxy-bismuth halides, and salts of bismuth anions are obtained by reaction of the alkoxide with an ammonium or phosphonium halide (28). Two isostructural derivatives [Bi2Cl4(thf)2(ju,-OAr)2] (Ar = C6H3Me2-2,6 and C6H2Me3-2,4,6) are composed of dimeric units residing on a C2 axis 8. The bismuth is in a five-coordinate distorted square pyramidal geometry in each case. The apical sites are occupied by terminal... 

Figure 28 Active site of the isopentenyl diphosphate isomerase enzyme from E. coli. In the crystals studied by Bonanno et al. the bidentate glutamate is monodentate and the Mn has a distorted square pyramidal geometry.

The structure of Rh(OMC)AsPh3 was determined by X-ray crystallography as shown in Fig. 11. It consists of discrete monomeric units where the rhodium atom has a distorted square pyramidal geometry. 

The interaction of the [Ph4P]+ salts of [Ru(0)2C13]-, [Ru(0)2C14]2 , and [0s(0)2Cl4]2- with excess tert-butyl isocyanate in acetonitrile forms the salts of the anions [MN Bu NC(0)NBu C12] (M = Ru or Os) (271). X-ray diffraction studies have shown the anions to have distorted square-pyramidal geometry with the nitrido groups in axial position [d(Os=N) = 1.629(7), d(Ru=N) = 1.588(6) A],... 

The characterization of complexes 55-58 involved IR, H NMR and 31P NMR spectroscopy and X-ray crystallographic analysis in the case of 55 and 56 [58]. The complexes are five-coordinate, adopting a distorted square-pyramidal geometry. The oxo group occupies the axial position and the equatorial plane is defined by the tridentate dianionic chelators and by the sulfur atom of the monothiolate. 

In the met form, the two ferric ions are bridged by an oxo ligand and the carboxylate side chain of a glutamate residue. The Fel atom has a distorted square pyramidal geometry, alternately characterized as pseudo-octahedral if the aspartate residue is assigned as chelating bi-dentate, whereas Fe2 has nearly perfect octahedral symmetry. In the active form of the enzyme, Tyr 122 has been oxidized to a tyrosyl radical (9), which, as revealed by the X-ray structure of met R2, is located in a hydrophobic pocket with its hydroxyl group 5.3 A away from Fel. The pocket does not contain any oxidizable side chains near the radical site... 

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