Carbonyl homometallic

Ligand fluxionality on metal clusters has been the subject of many studies, the majority of reports focusing on carbonyl migration on homometallic tri- and... 

Relatively few investigations involving palladium carbonyl clusters have been carried out, partly because palladium per se does not form stable, discrete homometallic carbonyl clusters at room temperature in either solid or solution states.114,917-922 Nevertheless, solution-phase palladium carbonyl complexes have been synthesized with other stabilizing ligands (e.g., phosphines),105,923 and carbon monoxide readily absorbs on palladium surfaces.924 Moreover, gas-phase [Pd3(CO)n]-anions (n = 1-6) have been generated and their binding energies determined via the collision-induced dissociation method.925... 

In a more general context, metal carbonyls on zeolites can be a unique way to prepare highly dispersed metal catalysts. In the present work, this is especially the case for iron as no other mild methods are operative. It is expected that the method could be applied to the preparation of bi- and polymetallic catalysts even though the starting material are not bi- or polymetallic clusters, but more conveniently homometallic clusters. 

Binding energy, pentacarbonyliron, 6, 3 Binuclear complexes bis-Cp titanium halides, 4, 522 with Ni-M and Ni-C cr-bonds heterometallic clusters, 8, 115 homometallic clusters, 8, 111 Binuclear dicarbonyl(cyclopentadienyl)hydridoiron complexes, with rand C5 ligands, 6, 178 Binuclear iridium hydrides, characteristics, 7, 410 Binuclear monoindenyl complexes, with Ti(IV), 4, 397 Binuclear nickel(I) carbonyl complexes, characteristics, 8, 13 Binuclear osmium compounds, with hydrocarbon bridges without M-M bonds, 6, 619... 

In most cases, bridged silylene complexes are homometallic owing to their synthetic methods, but a heterometallic complex can be prepared by the reaction of a hydrosilyl complex with a metal carbonyl [Eq. (II)].36... 

A few homometallic HNCC have also been produced by the condensation reactions of anionic carbonyl clusters with cationic complexes. For instance, sequential buildup of rhodium HNCC via incorporation of Rh(CO)2 fragments has been achieved by reacting [Rh(CO)2(MeCN)2] in acetonitrile with a series of anionic rhodium clusters as illustrated by the reactions shown in Eqs. (11) and (12) (223). 

The surface reaction of impregnated mixed metal cluster complexes may be analogous to that of homometallic clusters on hydrated and dehydrated metal oxides as described in Sections III and IV. Bimetallic clusters are converted to anionic surface species by simple deprotonation via 0 on dehydrated MgO or AI2O3 surfaces these species have been characterized by IR spectroscopy (119). The ionic interaction with surface cations such as AF and Mg is demonstrated by IR and NMR measurements. The surface polynuclear carbonyl anions are stable up to about 373 K. If heated in vacuo at higher temperature, extensive decomposition takes place to give a mixture of Ru (or Os) metal particles and Fe oxides, accompanied by the evolution of H2, CO, and CO2. 

Table 1. The largest homometallic carbonyl cluster species within groups 7-10.

From an in situ spectroscopic and chemometric view point, the lack of measurable quantities of Rh2(CO)g and Rh6(CO)ig in heterobimetallic CBERs is one of the most obvious differences with homometallic rhodium hydroformylations. This is clearly related to the very aggressive nature of the hydrides HMn(CO)5, HRe(CO)5, HWCp(CO)3 and HMoCp(CO)3 towards higher nuclearity rhodium carbonyls. It also suggests that in the heterobimetallic systems, there is slightly better utilization of rhodium due to the deduced concentrations of these di- and multinuclear reservoirs. 

Numerous metal carbonyl triangles formed by trimer-ization of 16-electron metal carbonyl fragments have been prepared. These include the homometallic trimetal dodecacarbonyls M3(CO)12 = Pe, Ru, and Os),... 

COMC (1995) provided many examples of clusters up to a C014 carbonyl example. However, as some polynuclear cobalt clusters with more than four atoms have been described during the last decade, the area of large cobalt carbonyl clusters seemed to have been much less investigated during this period of time. Nevertheless, several interesting examples of homometallic cobalt clusters with 5-18 cobalt atoms have been reported. 

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