Octahedron angular coordinates

Angular coordinates (0,

[Pg.198]

The tetrahedron (Tj) is considered here only theoretically, since CN=4 is too low for lanthanide systems. But it is interesting to compare both octahedron, cube and tetrahedron. The fourfold inversion axis or the threefold rotation axis can be chosen as z-axis. The angular coordinates are given in table 12. The PCEM expressions for the parameters with regard to the fourfold rotation axis are ... 

Tabie 2. AOM parameters and angular variables for hexa-coordinated complexes where the first coordination spheres [MAg] (A = N, O, Cl) show an octahedral or trigonally distorted geometry. The lower symmetries may be induced, for example, by the chelate geometry or by impacts due to the crystal lattice. The symmetry of the LF potential may be reduced if non-isotropic rr-bonding is apparent The actual structure of the [MAj] entity is very near to an octahedron. For planar chelates ip is not independent from 6 and

complexes investigated in this contribution... 

Other coordination polyhedra with D41, symmetry are the tetragonal bipyramid (CN = 6), which can be seen as a distortion of the octahedron, and the bicapped square prism (CN=10). The tetragonal bipyramid is not discussed here, because an angular distortion cannot lower the symmetry to D4. The distortion scheme of a bicapped square prism (BSP, D4h) to a bicapped square antiprism (BSAP, D4d) is analogue to the one described above. The PCEM expressions for the B and 5 parameters will be exactly the same as for the SP-SAP distortion scheme, since axial ligands do not have an influence on... 

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