Monocapped trigonal bipyramid tetrahedron

The monocapped trigonal bipyramid is the same as a bicapped tetrahedron (23.29). 

Rh9(CO)2iP]2+ monocapped square antiprism with interstitial P Fe3(CO)9C2BFl3, octahedral Co3(CO)9Bi, tetrahedron HRu3Fe(CO)i2N, butterfly with interstitial N or trigonal bipyramid depending on the butterfly deltahedral angle Fe3(CO)i2(CH)As, trigonal bipyramid. 

The availability of d orbitals on transition metal vertices leads to the possibility ofelectron-poor or hypoelectronic transition metal clusters with n vertices having less than 2 -I- 2 apparent, skeletal electrons. Such electron-poor clusters form deltahedra containing tetrahedral chambers, i.e., deltahedra with one or more vertices of degree 3 (Figure 9). The simplest examples of such deltahedra are the capped tetrahedra, of which the trigonal bipyramid (i.e., the monocapped tetrahedron) with five vertices is the smallest. The capped tetrahedra consist of a series of fused tetrahedral chambers with faces in common. An example of a cluster based on a bicapped tetrahedron is... 

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