Capped octahedron coordination

Capped argon stirring (CAS), 23 264 Capped octahedron, geometry for metal coordination numbers, 7 574, 575t Capped square antiprismatic, geometry for metal coordination numbers, 7 574, 575t... 

Fig. 8.4. Coordination geometries for seven- and eight-coordination (a) pentagonal bipyramid, (b) capped trigonal prism, (c) capped octahedron, (d) cube, (e) square antiprism and (/) triangulated dodecahedron. Central atom-ligand bonds are shown by full lines dashed lines indicate the edges of the polyhedral figure.

There are many complexes of lanthanides of coordination number seven [11]. There are many polyhedra for this coordination number, namely pentagonal bipyramid (Dsh) capped octahedron (C3V), tetragonal base trigonal base (Cs), capped trigonal prism (C2V) and capped trigonal prism (C3V). Inter ligand repulsivities have been studied as the function of the form of power law used for energy comparisons between different polyhedra for several coordination numbers [45,46], The order of preference for the different idealized... 

Figure 1-3 The three important geometries for seven coordination (a) Pentagonal bipyramid ( >5A) (b) Capped octahedron (C3 ) (c)...

The structures are known for a number of these compounds thus, of the eight-coordinate compounds, Eu(acac)3(phen) is square antiprismatic, Eu(dpm)3(py)2 and Nd(tta)3(Ph3PO)2 are dodecahedral seven-coordinate Lu(dpm)3(3-picoline) is a face-capped trigonal prism and Eu(dpm)3(quinuclidine) a capped octahedron. Nine-coordination is found in Eu(dpm)3(terpy) and also in Pr(facam)3(DME)3(facam = 3-trifluoroacetyl-D-camphorate). 

The starting point for the consideration of seven coordination is three stmctures with very similar stabilities the pentagonal bipyramid, capped octahedron, and capped... 

Tlie Re complexes, generally prepared by X2 oxidative addition to the parent Re species (equation 6), are normally seven coordinate and diamagnetic with a capped octahedron structure, but six-coordinate, 16-electron derivatives have been found, especially with isocyanide ligands. see Structure Property Maps for Inorganic Solids). 

Amines, hydrazines, and hydroxylamines. Amine complexes are known for tetravalent complexes of the earliest actinides (Th, U), particularly for the halides, nitrates, and oxalates. The complexes are generated either in neat amine, or by addition of amine to the parent compound in a nonaqueous solvent. Some of the known simple amine compounds are presented in Table 6. The molecular structure of ThCl4(NMe3)3 has been determined. The coordination environment about the metal is a chloride capped octahedron. A very limited number of adducts exist in which a tetravalent actinide is coordinated by a hydrazine or hydroxylamine ligand the parent compound is generally a halide or sulfate complex. Cationic metal hydrates coordinated with primary, secondary, or tertiary amines have also been isolated with acetylacetonate, nitrate, or oxalate as counterions. 

The three low energy structures available to 7-coordinate compounds are the pentagonal bipyramid, the capped octahedron and the capped trigonal prism. These structures are illustrated in Fig. 24. 

The application of moments of inertia to the study of 7-coordinate complexes is complicated by the low symmetry of the capped octahedron and the capped trigonal prism, which belong to the C3v and C2v point groups respectively. Only in the pentagonal bipyramid (D5h) are all the inter-ligand angles defined by symmetry. The capped octahedron and capped trigonal prism have... 

Pentagonal Bipyramid Capped Octahedron Capped Trigonal Prism Fig. 24. Low energy structures of 7-coordinate complexes... 

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