Pentagonal clusters

Figure 7. Stereo diagram of water pentagons, typical of those found packed to hydrophobic clefts in the protein crambin. The left-hand pair is for viewing with stereoviewers, while the right-hand pair should be viewed with the cross-eyed view. The pentagon cluster has the darkest lines. From ref. 171.

O—D stretching vibrations of water. This figure is modified from Kandori [98]. (A) Schematic drawing of the deuterated pentagonal cluster structure in the Schiff base. The numbers are the O—D stretching frequencies of water molecules in cm 1 assigned in the FTIR study. This figure is reproduced from Shibata and Kandori [95],... 

Other met-cars that have been detected mass spectrometrically are MgC (M = V, Zr, Hf) and there is some evidence for higher members such as Zri3C22, Zri4C23, ZrigC29 and Zr23C32 which may feature fused clusters of clusters. The possibility of a super-pentagonal cluster, M30C45, of Dsh symmetry has also been mooted. ... 

Pentagonal clusters. For each coat protein one has six decamers with symmetry 52 and 12 pentamers with symmetry 5 about the fivefold axis. The enclosing... 

Carbon is known with all coordination numbers from 0 to 8 though compounds in which it is 3- or 4-coordinate are the most numerous. Some typical examples are summarized in the Panel (p. 291). Particular mention should also be made of hypercoordinate non-classical carbo-nium ions such as 5-coordinate CHj", square pyramidal CsHs (cf. the isoelectronic cluster B3H9, p. 154), pentagonal pyramidal C6Me6 " (cf. iso-electronic Bf,Hio, p. 154) and the bicyclic cation 2-norbomyl, C7H] 1... 

The absence or very low intensity of 111, 311, 331, 333 and 511 indicates that clusters of atoms, perhaps 13-20, occupy the centres of the hexakaidecahedra, around iij and so on. There are also smaller clusters, probably of four atoms, inside the pentagonal dodecahedra, increasing the number of atoms in the 25.73-A cube to between 1,120 and 1,176. The composition of the alloys may be changed from MA16 by these additional atoms. 

An Au cluster with seven metals is found in [AnyCPPh,),]" (VIII). The Au core is a pentagonal bipyramid. ... 

Keywords Valence electron rule, Metal ring, Metal cluster, AN +2 valence electron rule, 8/V +6 valence electron rule, 6N +14 valence electron rule, Pentagon stability, Cyclopentaphosphane, Hydronitrogen, Polynitrogen, Triazene, 2-Tetrazene, Tetrazadiene, Pentazole, Hexazine, Nitrogen Oxide, Disiloxane, Disilaoxirane, 1,3-Cyclodisiloxane, Metallacycle, Inorganic heterocycle... 

This outstanding behavior of bis(pentamethylcyclopendienyl)stannylene has been explained by the energetically favorable formation of the ionic compound 79 which contains the 6-membered cluster C5Sn 174>. The structure of the boron tetrafluoride compound is illustrated in Fig. 15 the tin atom in the cation is located at the apex of a pentagonal pyramide 173). 

Platinum forms a wide variety of clusters and these are of interest as models for metallic platinum surfaces and catalysis on such surfaces. Many of these clusters are based on stacked triangles23,571 or bicapped pentagonal prisms.571 Many smaller clusters are also derived from triplatinum building blocks.16... 

Figure 18. Model showing the possible bridging of four rc-bonding molecules (C2H4) across two metal atoms of each pentagonal ring. Taken with permission from NATO ASI Series on Large Clusters of Atoms and Molecules Kluwer Academic Dordrecht, 1996, pp 371-404.

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