Coordination geometry tricapped trigonal prism

The malonate complex of Eu(III), Eu2(malonate)3 8H2O is interesting since there are two different coordination geometries, and only five of the water molecules are coordinated [167], One of the Eu ions is eight-coordinate in the form of a distorted square antiprism and the other Eu ion is nine-coordinate, distorted tricapped trigonal prism. In the analogous neodymium complex, six water molecules are coordinated because of the difference in ionic radius. The neodymium complex is nine-coordinate with monocapped antiprismatic geometry [168]. 

As is common with the higher coordination geometries, the interconversion of Dzh Cav niay be easily achieved. The monocapped square antiprism (C4 ) can be generated from the s-tricapped trigonal prism by raising the points a and b (Fig. 27) and lowering the two caps c and d so that the four form the basal plane of the square antiprism. 

A by-product of the preparation of U(Et2NC02)4 from the tetrachloride and the amine is a product of composition U402(Et2NC02)i2 this is a tetramer in which there are two non-equivalent uranium(lV) sites. In one of them the coordination geometry is a distorted tricapped trigonal prism, and the geometry of the other does not fit any type of regular polyhedron.1 5... 

The geometry of the nine-coordinate thorium atom in the thenoyltrifluoroacetonate complex, [Th CF3COCHCO-(2-C4H3S) 4 (n-CsHi7)3PO ], is a 4,4,4-tricapped trigonal prism (Figure 7).124... 

A second form of Nd2(malonate)3 6H2O complex has been reported [169]. In this complex neodymium is nine-coordinate surrounded by six carboxylate, and three water oxygen atoms and the geometry is intermediate between the distorted capped square antiprism and the distorted tricapped trigonal prism. 

Figure 10.3 Coordination geometry of a tricapped trigonal-prism (TTP) and a capped square-antiprism (CSAP) form of Gd-DTPA and Gd-DOTA, respectively [14].

Among other coordination spheres which may be chiral, there is the trivial case of the cA-hw-bidentate octahedral systems such as ciy-[Co(en)2Cl2], 6is-bidentate tetrahedral [M(A-A)2] or Z A-tridentate octahedral [M(A-A-A)2] complexes where the dihedral angle between the two chelate planes is different ih>m 90°, as is often the case. An example, together with the tns-tridentate [M(A-A-A)3] tricapped trigonal prism geometry often found for lanthanide complexes, is shown in Figure... 

Structural pictures of the systems studied. A detailed analysis of the first coordination shell [67] showed that for the light lanthanide ions (Nd " "), the nine water molecules form a tricapped trigonal prism similar to that found by solid state X-ray diffraction studies on [Ln(H20)9] + with counterions CF3SOJ, EtOSO, and BrO [68j. The eight H2O molecules in contact with the smaller heavy lanthanide ions (Yb +) form a square antiprismatic geometry with equal ion-oxygen distances. 

Hydration shells from simulations of Sm " " are actually a mixture of equal amounts of eight- and nine-fold coordinated ions adopting the geometry of a square antisprim or a tricapped trigonal prism, respectively [67]. Figure 4.8 (bottom) gives an example of the trajectories of the water molecules in the first and... 

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