Lead clusters

In addition to the C4V structure of the M(CO)3E9 ions shown in Fig. 5, a second isomer has been characterized for both the tin and lead clusters. Sn9W(CO)3" and Pb9Mo(CO)3 have both been isolated in a Cs structure in which the M(CO)3 fragment occupies a 5-coordinate waist vertex site instead of the 4-coordinate capping site shown in Fig. 5 [55, 60]. Both of these isomers give the same NMR spectra, which is consistent with the higher symmetry 4 structures. We interpret these data to indicate that there is local exchange between the 4-coordinate and 5-coordinate sites, but this interpretation is controversial [34, 55]. 

In the case ofn-Ge(lll) substrates, surface states affect electrochemical deposition of Pb [319]. At high cathodic potentials, the deposition occurs by instantaneous nucleation and diffusion-controlled three-dimensional growth of lead clusters. Comparing H- and OH-terminated n-Ge(lll) surfaces, the nucleation is more inhibited at n-Ge(lll)-OH, which can be explained by the different densities of Ge surface free radicals, being nucleation sites. In this case, nucleation site density is about 1 order of magnitude lower than that for n-Ge(lll)-H. 

The paper is divided in two parts. First (Sections 2 and 3), we have focussed our attention on the behaviour of pure lead clusters. Those clusters have been the subject of intense experimental research. Then, we consider that an ab initio study of small Pbn clusters would be useful for understanding the Pb-Pb bonding. The second part of the paper (Sections 4 and 5) is dedicated to the study of mixed Na-Pb clusters. 

Ruthenium-lead clusters 116 and 117 containing bridging Pb atoms were obtained from the reaction of the plumbylene [Pb CH(SiMe3)2 2] with Ru3(CO)i2 in hexane at 60 °C. Both clusters have a planar Ru3 triangle with bridging Pb and carbonyl ligands513. 

There are a limited number of structures reported for Fe—Pb complexes and these are recorded in Tables 16-18. For a series of iron carbonyl lead clusters, the Fe—Pb bond lengths vary from 2.624 A for an electron-deficient three-coordinate planar Pb cluster [FefCO jjPbl to 2.828 A for a tetrahedral bridging anionic Pb cluster... 

Since this article was written, several notable developments in organolead chemistry have been reported. New diplumbenes, a W-Pb triple bond, a tri(trisbiphenylplum-byl)lead anion, and new lead clusters have been obtained. 

The chemical shift of only has been observed at —4152 ppm (reference (CH3)4Pb) [24]. This fluxional cluster will be presented in more detail with the heteronuclear tin-lead clusters Sn9 jPbi in Section 4.6. 

Figure 8.15 Plot of experimental and theoretical electron affinities of carbon silicon, germanium tin, and lead clusters versus number of atoms. The experimental data are from [12, 45-54],...

Table 24.5 (continued) BDEs in Lead Clusters/Complexes... 

For these and other reasons it is no wonder that metal cluster chemistry has attracted the attention of some of the brightest minds in science over the past several decades and continues to flourish in so many ways. In this volume some of the leading cluster chemists provide up-to-date reviews of their fields of research. The topics covered include virtually every aspect of cluster chemistry with the notable exception of early transition metal clusters with r-donor ligands, which was the subject of a recent book.FJ... 

Doye, J. P. K. (2006). Lead clusters Different potentials, different structures. Computational Materials Science, 35, 227. 

Major logistics clusters have emerged arotmd the world. Leading clusters include Singapore, Rotterdam, Panama, Dubai, and Los Angeles. Because of the economy of scale, it is possible to develop and maintain specialized knowledge bases at the clusters. Clusters also enable the use of large ships for consolidation of shipments. 

---