Tetragonally elongated octahedron

Figure 3.21 Ligand field energy separations for Fe2+ ions in a tetragonally elongated octahedron (compare fig. 3.13). The inverted diagram applies to Mn3 in a similar environment.

Cation Electronic configuration Octahedron (regular) (pyroxene Ml) Tetragonally elongated octahedron (olivine Ml) Trigonally compressed octahedron (olivine M2) Monoclinic six-coordinated site (pyroxene M2)... 

The synthesis and structure of bis-(2,4,6-trichlorophenolato)di-imidazolecopper(n) monohydrate is reported and claimed to be a possible model for copper binding in transferrins. The copper is at the centre of a tetragonally elongated octahedron two imidazole N and two phenolic O atoms occupy the corners of a plane and O and Cl atoms occupy axial positions. Copper(ii) and bismuth(iii) and lead(n) complexes of hydroxyethylenediaminetriacetic acid have been studied CuHL and CuL formation was suggested. ... 

Complex Compressed tetragonal bipyramid Octahedron Elongated tetragonal bipyramid... 

This much greater tetragonal elongation of the octahedron has been... 

The tetrahedral or tetrahedral-distorted polyhedra are preferable for azo-methine chelates with coordination number 4 and coordination unit MN4 (868, X = NR, M = Co, Ni, Cu) [100,130,134,135,141]. At the same time, there are some suggestions for complexes 868 (X = NTs), according to whether the penta- (CN= 5) or hexa-coordinated (CN = 6) structures (tetragonal pyramid, elongated octahedron, mono- or two-capped tetrahedron) exist in them. The additional ligation of tetra-... 

A converse situation exists whereby the two oxygen ions along the z axis may move closer to the Mn3+ ion (fig. 2.8 >). This results in the stabilization of the dx2 y2 orbital relative to the dz2 orbital, and shorter Mn-O distances along the z axis compared to the x-y plane. In either of the tetragonally distorted environments shown in fig. 2.8 the Mn3+ ion becomes more stable relative to a regular octahedral coordination site. In most minerals, however, the Mn3+ ion occurs in an axially elongated octahedron (see table 6.1). 

Figure 3.13 Crystal field states and electronic configurations of Fe2+ ions in regular octahedral and tetragonally distorted octahedral sites. The tetragonally distorted octahedron is elongated along the tetrad axis.

Figure 6-41 illustrates the tetragonal elongation and compression of an octahedron. For the Cu2+ ion the relative energies of the dy and dy y2 orbitals depend on the location of the unpaired electron. 

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