Activation, of carbonyl clusters

Activation, of carbonyl clusters, 30 144-146 Activation analysis, charged particles and, 1 339-341... 

A catalyst of diisobutylene hydroformylation was synthesized by interaction of Rh2(CO)4Cl2 with nitrogen-containing polymer ligands obtained by treating chloromethylated copolymers of styrene and DVB with primary, secondary and tertiary amines [255]. The effect of diamine or substituted pyridine-type additions on the activity of carbonyl clusters of Rh was studied on RhgfCOIie during a... 

The reactivity of carbonyl clusters can be enhanced substantially by the use of their activated derivatives which contain such labile ligands as acetonitrile, ethene, or cyclooctene. For example, it was the synthesis of acetonitrile derivatives Os3(CO)12 x(NCMe)x (x = 1,2)1 that spurred the development of the chemistry of this trinuclear cluster.2-4 In general, the reactions of the activated clusters occur under mild conditions and result in high selectivities and yields. 

The substitution of an appropriate number of nitric oxide ligands for carbon monoxide is one possible method of activating metal carbonyl clusters for homo-... 

E5.10 Synthesis and catalytic activity of carbonyl palladium clusters... 

Protonation and deprotonation reactions of carbonyl cluster species are in general rather slow. A screening effect of the carbonyl groups around the metal nucleus which makes the direct interaction of the reactants difficult is considered to be the cause of large activation barriers. 

An early stimulus to cluster chemistry was the cluster-surface analogy, wMch proposed that cluster chemistry would resemble the surface chemistry of metals because both surfaces and clusters consist of arrays of metal atoms. Si ported metals such as Pd/C are very active catalysts. Carbonyl clusters have so far not shown the high catalytic activity of either metal surfaces or mononuclear homogeneous catalysts, probably because clusters are poisoned by the presence... 

The activation of silylene complexes is induced both photochemically or by addition of a base, e.g. pyridine. A similar base-induced cleavage is known from the chemistry of carbene complexes however, in this case the carbenes so formed dimerize to give alkenes. Finally, a silylene cleavage can also be achieved thermally. Melting of the compounds 4-7 in high vacuum yields the dimeric complexes 48-51 with loss of HMPA. The dimers, on the other hand, can be transformed into polysilanes and iron carbonyl clusters above 120 °C. In all cases, the resulting polymers have been identified by spectroscopic methods. 

Abstract This review is a summary of supported metal clusters with nearly molecular properties. These clusters are formed hy adsorption or sirnface-mediated synthesis of metal carbonyl clusters, some of which may he decarhonylated with the metal frame essentially intact. The decarhonylated clusters are bonded to oxide or zeolite supports by metal-oxygen bonds, typically with distances of 2.1-2.2 A they are typically not free of ligands other than the support, and on oxide surfaces they are preferentially bonded at defect sites. The catalytic activities of supported metal clusters incorporating only a few atoms are distinct from those of larger particles that may approximate bulk metals. 

These types of clusters represent some of the more modest sizes and geometries detected in homo- and hetero-metal carbonyl clusters. From dimetallic up to pentadecametallic clusters have been defined by crystal structures, and assembly of the metal centers in these clusters adopt a number of well-defined arrangements.83 Redox activity in these polymetallic clusters is anticipated and has been observed. Routes to large carbonyl polymetal clusters have been reviewed 83,84... 

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