Bicapped trigonal prism

Figure 1.3 Orientation of the g tensor of with respect to the Co-C-N-Ce plane (b). Ce3+ in [Ce(dmf)4(H20)3( i-CN)Co(CN)5] with For both figures, each component of the ten-respect to the bicapped trigonal prism of the sor is proportional to its respective modulus, coordination sphere of Ce3+ centre (a), and (After Ref. [53], Wlley-VCH.)...

Octacoordination is often encountered in lanthanide complexes. The preferred poly-hedra for eight coordination expected on the basis of interligand repulsivities are square antiprism (D ), dodecahedron with triangular faces (Z)2d), bicapped octahedron (D3(i), truncated octahedron (Z)2ft), 4,4-bicapped trigonal prism (C2v), distorted cube (C2v), and cube (0/,). The most commonly observed polyhedra for this coordination number are, however, the square antiprism and the dodecahedron. 

Other Nd—O distances are Nd—0(3) =2.35 A and Nd—0(4) =2.33 A (129). The separation between two neod miiums is 4.234 A. However, the ultraphosphates (P5O14) of Nd(HI) and Sm(HI) containing MOg units have a different structure (129,130). The coordination polyhedra is best described as being bicapped trigonal prism (see next section). 

Fig. 26. Dimensions of the irregular bicapped trigonal prism around octacoordinated So(III) in [HSc(trop)4]2. The vertical dotted line indicates the approximate 4 axis to illustrate the distortion of this polyhedron towards a dodecahedron...

The lanthanide sulphides show pol5unorphism and contain mixed coordination polyhedra and coordination numbers. The sulphides of La—Dy M2S3) form orthorhombic (A-t5q)e) crystals, where there are two kinds of nonequivalent cations (229, 230), one is heptacoordinated (monocapped triangular prism), and the other is octacoordinated (bicapped trigonal prism). Monoclinic (D-type) sulphides are formed by Dy—Tm and Y (229, 231) and contain both hexacoordinated and heptacoordinated lanthanide ions. The rhombohedral (E-type) sulphides of Yb and Lu contain only hexacoordinated metal ions (229). 

In the gas phase BiCl3 is a pyramidal molecule with d(Bi—Cl) 2.48 A and Cl—Bi—Cl 100°.220 In the crystalline state there are five additional near neighbours giving a bicapped trigonal prism for the bismuth atom (Table 30). 

Bicapped trigonal prism TlZrF5, (N2H6)ZrF6... 

FBP = pentagonal bipyramid CTP = C , monocapped trigonal prism CO = monocapped octahedron DD = dodecahedron SAP = square antiprism BTP = bicapped trigonal prism. 

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