R-mode clustering

Fig. 10. R-mode cluster analysis of the Pacific Northwest rainwater study (24). Reprinted with permission.

A variety of multivariate techniques (Q-mode and R-mode cluster analysis. Principal component analysis (PCA) and Detrended Correspondence Analysis (DCA)) were... 

Figure 30.5 Q-mode (collections) and R-mode (genera) cluster analysis, using the Jaccard coefficient, of abundance data from Patzkowsky s (1995) field data and field data from the Mitchell Siltstone Member (Candela, 2000) key for taxa as on Fig. 30.2.

By using the classical theory of ion induced nucleation to describe the growth of radon daughters from the free activity mode to the nucleation mode, we loose information about the size of the subcritical clusters. These clusters are all lumped together between the size of a pure H2O ion cluster at 75% r.h. and the size of the critical H2O-H2SO4 cluster. The model only does keep track of the growth by condensation of the radon daughters once they arrived in the nucleation mode. 

The 2,2 -bipyrazine (bpz)-substituted RU3 cluster monomer 42, dimer 43, and trimer 44 could be accessed by reaction of triruthenium precursor 2 with different amounts of 2,2/-bipyrazine [30]. The trimeric species 44 containing two parent Ru30(0Ac)6(py)2 n m and one derivate Ru30(0Ac)5(py)2II m m units could be directly prepared by reaction of 3.8 equivalents of 2 with 2,2/-bipyrizine. It is also accessible by reaction of dimeric species 43 with 1.8 equivalents of 2. The bpz adopts ri1 (N),(x-r 1 (N),r(1 (N) and p,4-r 1(N),r 1(N),r 1(C),r 2(N,N) bonding modes in 42, 43, and 44, respectively. Reduction of 3+ trimer 44 by addition of aqueous hydrazine allowed isolation of neutral intracluster mixed-valence species 44b containing three Ru 11,111,11 units. Oxidation of 44b with two... 

R. Wugt Larsen, P. Zielke, and M. A. Suhm. Hydrogen bonded OH stretching modes of methanol clusters A combined IR and Raman isotopomer study. J. Chem. Phys. 126, 194307 (2007). 

On the other hand however, the cluster-anions P7 and Pii are thermally remarkably stable. In the condensed state (in the crystal as well as in melts), the characteristic vibrations can be observed both in i.r. spectra and in Raman spectra upto temperatures of 900 K (25, 26,27). As an example, the Raman spectra of Ha3P7 in Figure 7 clearly show that the typical cluster-vibrations of the P7 -anion are maintained up to the region of the plastic phase, although the absorption bands become increasingly broader and less distinct with temperature. The lattice vibrations at 50-100 cm " behave completely differently. As expected they disappear at the transition to the plastic phase. Completely unexpected however, they remain sharply resolved up to the critical temperature Tc. This effect can be connected with the presence of two undamped lattice modes (25). 

Heating 26 with an excess of PPhj under pressure in chlorobenzene leads to the loss of one coordination site. One more Os-Os bond is broken upon formation of the complex Os3(CO)6(CNR)(p3-CNCH2QH4)-(PPh3)(p-PPh2)(p-T r -C6o) [74], The T r binding mode observed in this complex is very unusual for Cg0. One further example, where can act as a four-electron ligand is the fullerene carbido pentaosmium cluster complex 28 shown in Scheme 7.13 [75,76], The ri T -complex 28 is formed in a mixture with the normal T r r carbido pentaosmium complex 27. The two complexes can be converted into one another at elevated temperatures. 

Penta- and hexanuclear clusters of the metals osmium and ruthenium coordinate with the same r ri ri - binding mode as the trinuclear clusters to CgQ. Such complexes are known for the clusters OsjC [75,76], RU5C [77-79], RugC [78], PtRu5C [77] and Rhg [80], In this collection of metal clusters rhenium plays a special role, because it forms a new fullerene-metal sandwich complex, where two C50 are bound to one cluster. 

The simultaneous function of a transition metal atom as a lone-pair acceptor and as a cluster vertex atom is realized in [(77 -Ge9)Cu(ry -Geg)] (Fig. 5j), in which the two [Geg]" units are connected in an r/ - and an r/" -fashion to the same Cu ion. Transition metal bridges between Geg clusters are also found in various other coordination modes in [Ge9(/i -Au)3Geg] (Fig. 5k), three bridging Au atoms each are coordinated by two Ge atoms of two different Geg units in an almost linear way and entertain aurophUic interactions within the resulting triangle of Au" " ions two [GegR3] anions are coordinated via their triangular face to ( M = Zn, Cd,... 

Table 9 SCF, second-order perturbation theory, and coupled-cluster values of the equilibrium bond length R, energy E, at R, and harmonic frequency w of the breathing mode of SnH .

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