Cluster exchange

Cluster Exchange Type Fluxiona] Process (Exchange Banicr) Ref. 

In this chapter, we will consider systems having small cluster exchange effects or even isolated paramagnetic behavior to be magnetic materials, because they... 

Table 3 Mixed Valence Clusters Exchange times of the pz bridged clusters (1) in different solvents times. vs. solvent inertial relation ... 

NiFeC signal, which displays hyperfine coupling to Ni, Fe, and [103, 104]. The Mossbauer spectmm indicates that this species contains a diamagnetic [Fe4S4] cluster exchange-coupled to a Ni(l)CO center, which is proposed to be the proximal site [105]. It remains unclear if the species responsible for the NiFeC signal is relevant to catalysis [106, 107]. 

Covalent. Formed by most of the non-metals and transition metals. This class includes such diverse compounds as methane, CH4 and iron carbonyl hydride, H2Fe(CO)4. In many compounds the hydrogen atoms act as bridges. Where there are more than one hydride sites there is often hydrogen exchange between the sites. Hydrogens may be inside metal clusters. 

The hydration of more inert ions has been studied by O labelling mass spectrometry. 0-emiched water is used, and an equilibrium between the solvent and the hydration around the central ion is first attained, after which the cation is extracted rapidly and analysed. The method essentially reveals the number of oxygen atoms that exchange slowly on the timescale of the extraction, and has been used to establish the existence of the stable [1 10304] cluster in aqueous solution. 

Pisani [169] has used the density of states from periodic FIP (see B3.2.2.4) slab calculations to describe the host in which the cluster is embedded, where the applications have been primarily to ionic crystals such as LiE. The original calculation to derive the external Coulomb and exchange fields is usually done on a finite cluster and at a low level of ab initio theory (typically minimum basis set FIP, one electron only per atom treated explicitly). 

Lover T efa/1997 Electrospray mass spectrometry of thiophenolate-capped clusters of CdS, CdSe and ZnS and cadmium and zinc thiophenolate complexes observation of fragmentation and metal, chalcogenide and ligand exchange processes Inorg. Chem. 36 3711... 

Thermal arene exchange of tetramethylthiophene with [(/ -cymene)RuCl2]2 affords 130 (89JA8828), which on reaction with AgBE4 and excess tetramethylthiophene yields 131. The Ru—S thiophenic cluster, 132, was synthesized by reaction of 130 with (Mc3Si)2S followed by anionic metathesis and formation of the PFg salt. The coordination geometry around each ruthenium atom is pseudooctahedral. 

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