Carbonyl clusters binuclear

This reaction is diffusion controlled in solid CO. The binuclear carbonyl is unstable and even at these low T decomposes to Ag2 or higher clusters. Similarly, Au forms Au(CO)[ or 2, which does not dimerize. However, Cu cocondensed with CO and Ar forms compounds Cu (CO) (n = 1-4), which after warming to 35 K decompose to larger Cu carbonyl clusters of indeterminate composition, the IR spectra of which resemble CO chemisorbed onto bulk Cu. 

The metal carbonyl clusters correspond to situations intermediate between metals and simple mononuclear or binuclear carbonyls. Their existence must be connected either with a delicate thermodynamic balance or with remarkably high activation energies. The last hypothesis is valid for species such as Rh6(CO)j6 which is kineti-cally inert, but in general we are inclined to believe that thermodynamic control is the more significant, especially since reactions, such as that shown in Eq. (1), can be carried out in both directions using mild conditions. 

These studies have Indicated that simple rhodium carbonyl complexes, e.g., mono- and binuclear species are Involved in the fragmentation and aggregation reactions of rhodium carbonyl clusters under high pressures of carbon monoxide and hydrogen. They indicate that it is possible to write formal equations for such reactions in the case of rhodium carbonyl anionic hydrido clusters (equation 25) and for the more particular situation when there are not hydrides present (equation 26)... 

A number of binuclear phosphine-ligand bridged complexes have been shown to function as catalysts or catalyst precursors. Here we review these cases briefly. More detailed coverage of hydrogenation and hydroformyla-tion using rhodium catalysts will appear in the next chapter. In all cases of catalytic activity shown by binuclear complexes, there is a serious question about the true identity of the catalytically active species. As with catalysis begun by metal carbonyl clusters, the possibility exists that a small amount of highly active mononuclear compound is the true catalyst. 

Nickel carbonyl radicals show an even greater tendency than cobalt carbonyls to cluster in a krypton matrix. Three binuclear nickel carbonyls have been detected by EPR spectroscopy in the products of y-irradiated Ni(CO)4 in Kr, yet no mononuclear species has been positively identified (65). 13C hyperfine structure has... 

Binuclear and polynuclear carbonyl complexes were among the first compounds containing M-M bonds to be prepared early in the present century, but it was not until the crystal structure determination of Mn2(CO)i0, i.e. (CO)5Mn—Mn(CO)5, in 1957 that such bonds were authenticated in carbonyls. The study of polynuclear carbonyl complexes has been a major growth area of chemistry since then. Clusters containing more than 50 M atoms have been characterised. Some examples are illustrated in Fig. 8.8. 

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... 

Reaction of Fe3(CO)12 with 3-pentyn-l-ol gives the hydrido cluster 4, formed by coupling of an allenylidene unit with a coordinated carbonyl ligand and methoxy group. In contrast, reaction with the isomeric alkyne 2-methyl-3-butyn-2-ol affords a binuclear iron complex.18 Treatment of Fe3(p3-S)2(CO)9 with Me3NO affords the vinylferrocene complex 5, whereas the similar reaction with Fe3(p3-Te)2(CO)9 gives no cluster products.19... 

A binuclear bis(/r-germylene) osmium carbonyl complex [(OC)40s(GeMe2)]2 on photolysis or thermolysis yields a mixture of an interesting series of (/z-germylene) osmium clusters . Bis(metalcarbonyl)germacyclopentene complexes on photolysis or thermolysis... 

Tungsten-Re and W-Ir binuclear carbene complexes as well as cluster carbene complexes are prepared via acylation-alkylation of the corresponding carbonyl compounds. 

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