Cluster fusion

Note that the common fragment appears to be a 22 eve butterfly fragment (like B4H10) rather than a ring isoelectronic with C4H8. We will encounter this ambiguity for metal clusters as well when cluster fusion involves four common atoms. 

Considering the fact that the number of polyaromatic compounds known is large, this result should be no surprise. Of course neither the mno rule nor the cluster-fusion rule by itself gives any insight on the synthesis of the compounds. But they do suggest many such fused systems should be possible to make and that is added justification for seeking their syntheses. 

Answer. The first step is to analyze the geometry and break the cluster down into smaller clusters from which it may be reassembled using the cluster fusion principle of Mingos. As shown in the second drawing above, the cluster can be viewed as a pentacapped Rh-centered cube hence, it may be assembled from a cube (120 eve, Table 3.1) and five square pyramids (74 eve). As shown above, the common fragment is a square and consultation of Table 3.1 indicates 64 eve. However, recall that a square can also be obtained from an octahedron by removing two non-adjacent vertices hence, it has 62 eve, which is the same as for a butterfly (removal of two adjacent vertices from an octahedron). So there are two possibilities 64 and 62 eve adding another variable to the mix. As shown below this leads to a prediction of eve = 170 or 180. The actual count is 180 (14 Rh + 26 CO + 2— = 126 + 52 + 2 = 180). 

The number of cluster valence electrons is 66. Based on the examples of metalloid clusters in the text, we don t expect the borane paradigm to work for this closed cluster and it does not (An + 2 = 58 eve). It can be viewed as a hexacapped three-connect (highly distorted) cube giving, via the cluster fusion rule 5 x 8 + 6 x 24 — 6 x 24 [or — 6 x 22] = 40 [or 52] eve. This doesn t work and besides, four of the cube edges have very long Sn-Sn contacts. Finally, it can be viewed with the modified Schleyer approach (no lone pairs on Sn atoms) or the Schleyer approach... 

Poupon, V, Stewart, A., Gray, S.R., Piper, R.C. and Luzio, J.P. (2003) The role of mVpslSp in clustering, fusion, and intracellular localization of late endocytic organelles. Mol. Biol. Cell 14, 4015-4027. 

Recently a series of monodisperse CdS clusters were synthesized by the method of controlled cluster fusion[36-39]. With this method, a well-defined single-size molecular cluster [Cd10S4(SPh),h]4 [54], was used as the... 

Fig. 4.17. Plot of cluster-fusion dissimilarity vs. step number in single-linkage clustering, indicating that step 96 is a suitable stop point (see text)...

The synthesis of (11) shows that the P geometry can spontaneously assemble from a cubane synthon, hydrosulfide, and reducing agent. The Fe protein is essential in the natural synthesis of working MoFe protein (see Section 8.22.5), suggesting that a similar reductive cluster fusion could... 

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