Five-vertex

Figure 26. A cube is decomposed into six five-vertex pyramids. The gray circles are the field...

A similar appraisal of the vertical middle row in Fig. 1 (the nido fragments) shows that basic process L also applies in all cases excepting that, in following low coordination vertex removal, bonds must be inserted in the ten- to nine-vertex and six- to five-vertex cases (process... 

The chlorocuprate(I) anion in [Co(NH3)6]4[Cu5Cli6]Cl, viz. [C115-Cli6]11, has been shown to be composed of five vertex-linked tetrahe-dra, i.e., a central CuCl4 unit linked via all four vertices to four cop-per(I) chloride tetrahedra (100,101). 

The structures of 13 (33), 14 (34), and 15 (35) are shown in Figs. 13, 14, and 15. Each of the products is a 76-electron five-vertex cluster in 13 the phosphorus ligand donates three electrons to the cluster, 14 is the trimethyl-phosphite substitution product of 13, and in 15 the phosphorus ligand contributes five electrons to the cluster. As with the isoelectronic [Os5C(CO)l5I]-, the Os5C cores take open structures based on a pentagonal bipyramid in which only three of the equatorial vertices are present. The structures of the Os5C cores are very similar for 13,14, and 15. Mean Os-Os distances are 2.90 0.06 A for all three, and the carbido carbon atom is... 

Os5(CO),6 N is found to be 9 for this complex, and the only five-vertex figure with nine edges is a trigonal bipyramid the observed structure has a slightly-distorted trigonal bipyramidal arrangement of Os atoms. 

The [GaBi3] ion has six pairs of electrons with which to bond four atoms. [GaBi3] is therefore classed as a nido-cluster, based on a five-vertex trigonal bipyramid with one vertex missing. This is consistent with the observed tetrahedral shape ... 

FIGURE 87 Structure of the pentadecanuclear cluster [EU)5(/t3-OH)2o(/t5-Cl) (/t3-Tyr)io(OH)2(/i-H20)5(H20)i8] (left). The wheel-like core structure showing five vertex-sharing cuboid [Eu4(/t3-OH)4] units centered on a /ts-Cl ion (right) (redrawn after Wang et al., 2001b). 

What happens when there are more atoms than vertices into which they can fit For example, Os6(CO)ig is a (6 x 2) = 12 cluster electron species. This means that the number of vertices required by Wade s rule is - l 5. The structure found for the molecule, 13.16, shows that the extra metal atom bridges to a face of the five-vertex base polyhedron, and so is able to contribute its electrons to the cluster, even though it cannot occupy a vertex. 

Figure 1.9 (a) Gale diagrams for the two five-vertex polyhedra. (b) Standard Gale diagrams for the seven six-vertex polyhedra. 

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