Carbonyl clusters with metal

The literature and our data give evidence for interesting possibilities of interaction of organometallic compounds with the surfaces of supported metals for obtaining bimetallic catalysts. The use of this novel reaction of metal carbonyl clusters with metal surfaces allows the second metal to be selectively supported on the surface of a metal particle under mild conditions. The bimetallic catalysts obtained have some advantages over conventional catalysts ... 

M ,(CO) Metal carbonyl clusters with bridging CO groups M-C(0) M... 

Table 25.9 Some metal carbonyl clusters with interstitial atoms...

Cabeza, J.A., in Braunstein, P., Oro, L.A., Raithby, P.R. (Eds.), Homogeneous Catalysis with Ruthenium Carbonyl Cluster Complexes Metal Clusters in Chemistry, Vol. 2. Wiley-VCH GmbH, Weinheim,... 

According to this approximation, in a metal carbonyl cluster each metal atom, like a BH unit, may effectively contribute only three orbitals to the skeleton, whereas the remaining six are left for bonding with the external ligands and for lone pairs, and are assumed to be completely filled. The... 

Molecularly or ionically dispersed metal carbonyl clusters on metal oxides have been prepared in high yields by reaction of metal carbonyl clusters with support surfaces or by syntheses on support surfaces from mononuclear precursors (Gates and Lamb, 1989 Iwasawa, 1993 Ichikawa, 1992 Gates, 1994). Synthesis of supported metal carbonyl clusters has been reviewed recently (Gates, 1995,1998), and only a few examples are included here. 

Although anionic species with nickel in the oxidation state -I have been postulated, such as [Ni2(CO)6]2, these have not been confirmed. Nickel does, however, form a number of anionic carbonyl clusters with higher nuclearity, e.g., [Ni5(CO)l2]2-, in which the metal carries a partial negative charge. 

Figure 25.13 Metal frameworks of some Ru and Os carbonyl clusters with interstitial atoms, (a) [Ru8(H)2(CO)2i] (octahedron and face-sharing trigonal bipyramid) the second H is probably at the centre of the octahedron. (b) [Ru8(C)2(CO)n(PPh2)2] (octahedron and face-sharing square pyramid) PPh2 ligands bridge the pairs of shaded Ru atoms, (c) [Os7(H)2C(CO)i9] (tetrahedron and 3 irregularly spaced metal atoms) H atoms probably bridge two edges of the tetrahedron.

This preparative method would appear to be a special set of the previous class of reactions (Section II,B>2), as there is considerable evidence that halocarbonyl compounds are intermediates in the formation of carbonyl clusters from metal halides. In the reaction of RhClg with CO in a methanol solution, the chlorocarbonyl dimer [Rh(CO)2Cl]2 has been isolated as an intermediate in the formation of Rh4(CO)i2 (79). 

Acetylenes are not the only compounds with organic tt systems which can substitute in metal carbonyls, and the same general synthetic methods can be used for other ligands. Reaction of carbonyl clusters with polyolefin systems, such as 1,5-cycloocatadiene and 1,3,5,7-cyclo-octatetraene, have produced substituted carbonyl systems, but only with Ru3(CO)i2 have clusters been isolated. Arene-substituted carbonyl clusters have also been obtained, as has been described in Section II.D.l. 

An example of electron counting in a metal carbonyl cluster with an interstitial atom is illustrated by Ruf,C(CO)i7, which has the 14 skeletal electrons required for a globally delocalized octahedron by the following electron-counting scheme ... 

C3.3 Metal carbonyl clusters with alkynes bound in parallel or perpendicular fashion... 

Bridges between trinuclear metal clusters [of Ru, Os] Synthesis of ruthenium and osmium carbonyl clusters with unsaturated organic rings Oxyligand derivatives of triosmium dodecacarbonyl... 

A number of examples, where two or more isomers of metal carbonyl clusters with identical metal core geometries and different ligand dispositions have been struc-... 

Halet J-F (1992) Theoretical aspects of the bonding in transition metal carbonyl clusters with interstitial main group atoms. In Gielen M (ed) Topics in physical organometallic chemistry, vol 4. Freund Publishing House, London, pp 221-288... 

Such simple HOMO-LUMO arguments, however, do not seem applicable to even slightly larger metal clusters. The redox potentials of a series of tetracobalt carbonyl clusters with different ligands were found to correlate well with the total... 

IR metal carbonyl clusters structures of metal carbonyl clusters interaction of metal carbonyl clusters with the zeolite framework Identifications of metal carbonyl dusters in cages are inferred from comparisons of their spectra with those of analogous molecular dusters in solution or in solid state most reliable for very small cluster shifts of carbonyl bands identify the interaction of carbonyl dusters with the zeolite framework. 

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