Transition metal clusters specific types

C-H Bond Activation. We have also examined the chemisorption of various hydrocarbons on different transition metal clusters. In this section we describe results obtained for methane activation on neutral clusters. First, we note that under our experimental conditions (low pressure, near room temperature, short contact time) methane activation readily occurs only on specific type and size metal clusters. For instance, we detect no evidence that methane reacts with iron(12), rhodium(26) or aluminum(2Z) clusters, whereas as shown in figure 5 strong size selective chemisorption is... 

Couple cluster methods differ from perturbation theory in that they include specific corrections to the wavefunction for a particular type to an infinite order. Couple cluster theory therefore must be truncated. The exponential series of functions that operate on the wavefunction can be written in terms of single, double and triple excited states in the determinantl " . The lowest level of truncation is usually at double excitations since the single excitations do not extend the HF solution. The addition of singles along with doubles improves the solution (CCSD). Expansion out to the quadruple excitations has been performed but only for very small systems. Couple cluster theory can improve the accuracy for thermochemical calculations to within 1 kcal/mol. They scale, however, with increases in the number of basis functions (or electrons) as N . This makes calculations on anything over 10 atoms or transition-metal clusters prohibitive. 

We have included not only pure nitride materials but also many amides, azides, oxynitrides (but not nitrates and nitrites), nitride chalcogenides, and nitride halides. Specifically excluded are polymeric compounds (e.g. SxNy), cluster compounds (e.g. Sc2C12N), coordination compounds (e.g. [Pd(NS3)2]), ternary azides and amides, as well as ternary interstitial transition-metal nitrides. We have attempted to include all important structures and all type compounds. This review is also unique in that we attempt to evaluate the... 

Of the 33 papers presented at the symposium 32 are included in this volume. They are of two general types. One type discusses inorganic compounds exhibiting a specific property, most frequently electrical or photochemical. The second type reviews recent developments in the synthetic chemistry of a class of inorganic compounds— most often transition metal or lanthanide complexes— which are of potential interest to persons looking for new systems with unusual properties. Classes of compounds covered by this second type include metal alkyls, metal alk-oxides, metal alkylamides, metal chelates, and metal clusters as well as metal complexes with polyboranes, polyphosphines, macrocyclic derivatives, di- and triketones, and polypyrazolylborates as ligands. 

A number of review articles have described the applications of multinuclear NMR methods for studying structures and internal rearrangements of metal clusters. The more specific cluster types covered were transition metal carbonyl clusters/ chiral clusters/ and mixed metal clusters containing carbyne or ketenylidene bridges. ... 

The ab initio determination of optically allowed transitions and their intensities for the most stable cluster structures is feasible in particular for simple metals (la) " as well as for mixed aggregates involving metallic, ionic, or polar bonding and combination, of these bonding types. A comparison of the theoretical predictions which are strictly valid at zero temperature with the spectra recorded at low temperature allows one to propose the assignment of the cluster structure to the measured features and to account for the specific character of small finite clusters. 

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