Cluster isomerization

Development of Coordination Chemistry Since 1930 Coordination Numbers and Geometries Nomenclature of Coordination Compounds Cages and Clusters Isomerism in Coordination Chemistry Ligand Field Theory Reaction Mechanisms... 

T. Haber, U. Schmitt, C. Emmeluth, and M. A. Suhm, Ragout jet FTIR spectroscopy of cluster isomerism and cluster dynamics From carboxylic acid dimers to N2O nanoparticles. Faraday... 

Bown M, Jelinek T, Stibr B et al (1988) Eacile pathway-defined fluxional cluster isomerization in 10- Vertex Closo-2,l,6-metalladicarbaboranes of ruthenium and rhodium. J Chem Soc Chem Commun 974—975... 

Figure 7. Upper panel Lowest energy equilibrium geometries and calculated adsorption energies of O2 and O4 on AgL clusters. Isomeric structures for n=4 and 6 are also depicted. Minimum distance O-Ag (middle panel) and 0-0 (lower panel) in the equilibrium structures of AgnO (circles) and Ag Oj (squares) clusters. The crosses indicate the distance Ag-O and 0-0 for the next nearest O2 adsorbed molecule in Ag Oj anions. The triangles at n=4,6 correspond to the near degenerate structures depicted in the upper panel.

The authors of this work did not consider I-IV as cluster compounds nor did they view II and IV as cluster isomers. Let us see if we can relate the observed chemistry to cluster isomerization albeit one in which the forward (C apart to C adjacent) and reverse (C adjacent to C apart) have similar barriers. That is, an effective alkyne metathesis catalyst cannot have any species in the catalytic cycle of high stability (Bunz, 2005). 

Having studied the classical dynamics of cluster isomerization in the liquid-like phase, we are now stepping into a new stage of statistical chemical reaction theory. However, before proceeding, we would like to explore temperature in general chemical reaction dynamics, since we could define well a temperature... 

Several reports dealing with metal-cluster isomerism and possible mechanisms of polyhedral rearrangements have recently been published. Although work in this field was first undertaken by Braunstein in 1991,no further studies have subsequently appeared. Given the increasing interest in cluster isomerism, the purpose of this article is to provide an updated systematic classification to facilitate the study of this area. 

In order to determine the rate constant for the cluster isomerization reaction from the temperature-dependent intensity ratios, one needs a model for the mechanism of the transformation. The simplest model for the isomerization of more cylindrically shaped clusters S1n° to more spherically shaped clusters SIn is based on the assumption that the cluster isomerization can be described by a... 

The activation enthalpy A // and the activation entropy A S can be derived from the temperature dependence of the A G values as a function of cluster size for N = 45-60 values of A iT=5kJ/mol and A iS -180 J/(K mol) are typical. This means that entropic effects play an important role in the cluster isomerization reaction, because the activation free enthalpies A G are an order... 

A convenient feature of the isomerization between the monolayer and stacked structures is the fact that the frequency shifts predicted for the fundamental V3 band of SFg are distinctly different for the two forms. In particular, the magnitude of this (negative) frequency shift is approximately proportional to the number of perturber atoms in direct contact with the SFg, so the magnitude of the shift becomes distinctly smaller when a cluster isomerizes from a monolayer to a stacked form. This provides both a simple property for monitoring the state of the system during a simulation, and a possible means of observing such transformations experimentally. 

Fanourgakis, G. S., Farantos, S. C., Parneix, R, 8c Brechignac, P. (1997). An effective transition state for a complex cluster isomerization process Comparison between anharmonic and harmonic models for mg ar - Journal of Chemical Physics, 106, 4954. 

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