Cluster molecules

Steigerwald M Let al 1988 Surface derivatization and isolation of semiconductor cluster molecules J. Am. Chem. Soc. 110 3046... 

Quite apart from the fullerene cluster molecules, numerous other molecular allotropes of carbon, C , have been discovered in the gases formed by the laser vaporization/supersonic expansion of graphite. The products are detected by mass... 

C.E. Housecraft, Cluster Molecules of the p-Block Elements. Oxford University Press, 1994. 

The schematic (Figure 9) for a drum indicates how it is related to two cluster molecules. Formally, two bridging phosphinates rearrange, two oxygen atoms are added, four Sn-0 bonds are cleaved, the six Sn-O-Sn linkages become Sn(OH)Sn units, and two phosphinates are added to hydrogen bond to the hydroxyls. 

A useful introduction to the structures of cluster molecules and the electron counting rules proposed by Wade and others. 

A metal cluster can be considered as a polynuclear compound which contains at least one metal-metal bond. A better definition of cluster catalysis is a reaction in which at least one site of the cluster molecule is mechanistically necessary. Theoretically, homogeneous clusters should be capable of multiple-site catalysis. Many heterogeneous catalytic reactions require multiple-site catalysis and for these reasons discrete molecular metal clusters are often proposed as models of metal surfaces in the processes of chemisorption and catalysis. The use of carbonyl clusters as catalysts for hydrogenation reactions has been the subject of a number of papers, an important question actually being whether the cluster itself is the species responsible for the hydrogenation. Often the cluster is recovered from the catalytic reaction, or is the only species spectroscopically observed under catalytic conditions. These data have been taken as evidence for cluster catalysis. 

The Semicrystalline Structure of Amylopectin. Amylopectin crystallises according to a cluster molecule,25 as shown in Figure 8b. Within this structure there are crystalline and amorphous regions. An... 

It has been noticed by a number of workers that the ligands L in cluster molecules MmL occupy positions which define (to a fair approximation) the vertices of regular and semiregular polyhedra. In... 

While Hirsch conceived his 2(n + l)2 electron rule for spherical aromatics, subsets of three-dimensionally aromatic molecules having very high symmetries ( Ti, Oj, h, etc.), it can be applied to lower symmetry clusters such as the nine-vertex examples above. In cluster molecules the highest degeneracy MOs of a spherically harmonic atom set split into related, but lower degeneracy (or even non-degenerate) components. 

The high pseudosymmetry of the cluster molecule 83, clearly shown in Figure... 

The distance between two cluster molecules is 1.3 nm, i.e., between the naked base and apex of gallium atoms of two clusters, whereby two parallel oriented toluene molecules bridge the intermediate space. Although four-point measurements for electrical conductivity in the temperature range 350 K to 2 K have been carried out, the mechanism of electron conductivity cannot be conclusively explained 83 is... 

In the light of several allotropic modifications known for phosphorus, the relatively high single bond energies and the tendency of phosphorus to catenate it remains mysterious, and that apart from P4 and As4 only very scarce information on isolated E cluster molecules is available from hard experimental data. In contrast, a vast amount of solid theoretical work has been performed [11],... 

Although no En cluster molecules with n > 4 are known in the condensed phase, it has been shown [27] that neutral P6 can be generated in the gas phase by neutralization-reionization mass spectrometry with cp 2 6 as a precursor [cp = C5(CH3)5] [28]. Since the cp 2P6 precursor molecule already has a hetero-benzvalene P6 skeleton, it was inferred that the neutral P6 molecule should have the benzvalene structure as shown in Figure 2.6-5. This is in agreement with a multitude of quantum chemical calculations [8, 11, 27, 29-32]. Note that the handle of the basket of P6 includes two dicoordinate P atoms linked by a P=P double bond (cf. R-P=P-R 203 pm [33]). 

On irradiation, the cluster molecule Os3(CO)12 is resistant to Os-Os bond cleavage and instead undergoes photosubstitution with a low quantum yield ... 

S. J. Green, J. J. Stokes, G. D. Wignall, G. L. GUsh, M. D. Porter, N. D. Evans, and R. W. Murray, Alkanethiolate gold cluster molecules with core diameters from 1.5 to 5.2 nm Core and monolayer properties as a function of core size, Langmuir 14,17—30 (1998). 

More advanced mathematical aspects of aromaticity are given in other references [33, 34]. Some alternative methods beyond the scope of this chapter for the study of aromaticity in deltahedral molecules include tensor surface harmonic theory [35-38] and the related Hirsch 2 N -b 1) electron-counting rule for spherical aromaticity [39]. The topological solitons of nonlinear field theory related to the Skyrmions of nuclear physics have also been used to describe aromatic cluster molecules [40]. 

This behavior differs completely from the discrete one-electron absorptions of low-nuclearity metal cluster molecules [17]. Instead, it resembles the 5d - 6s,6p interband transition of colloidal gold. This demonstrates clearly that the AU55 cluster has electronic energy levels which are closely spaced in a developing band structure, quite similar to colloidal gold. On the other hand, these electrons do not seem to show a collective behavior which would give rise to the plasma resonance. 

Hostetler MJ, Templeton AC, Murray RW. Dynamics of place-exchange reactions on monolayer-protected gold cluster molecules. Langmuir 1999 15 3782-3789. 

Templeton AC, Wuelfing MP, Murray RW. Monolayer protected cluster molecules. Acc Chem Res 2000 33 27-36. 

Steigerwald ML, Alivisatos AP, Gibson JM, Harris TD, Kortan R, Muller AJ, Thayer AM, DimcanTM, Douglass DC, Brus LE (1988) Surface Derivatization and Isolation of Semiconductor Cluster Molecules. J Am Chem Soc 110 3046-3050... 

---