Octahedral clusters metal carbonyls

Similar bonding descriptions are possible for the other octahedral metal carbonyl clusters. In Rha(CO)i6, for example, 4 electron pairs can be allocated to the four metal-carbon bonds each metal atom is involved in (each metal has two terminal and two triply bridging... 

HOs6(CO)18] and H2Os6(CO)18 marks one of the highlights of the early period of osmium carbonyl cluster chemistry [162]. While both the dianionic cluster and the monoanionic system have the expected octahedral metal core, a capped square based pyramidal structure was found for H2Os6(CO)18. This turned out to be the archetypal example for the capping rule , a concept which proved to be very successful in the analysis of the structures of metal carbonyl clusters of the iron and cobalt triads [166],... 

The versatility of transition-metal-ligand combinations in stabilizing localized, partially localized and delocalized cluster bonding is evident in the three examples discussed to this point. But we still have no analog of a late metal-carbonyl cluster that follows the main-group counting paradigm for an octahedral shape. Centered zirconium chloride clusters provide an example of an octahedral cluster with seven... 

Although the above mentioned face- and edge-halide-bridged clusters are characterised by 84 and 76 valence electrons respectively, it was apparent by the early 1970 s that the great majority of octahedral transition metal clusters possess 86 electrons. Braterman rationalised the 86 cluster valence electron count for octahedral metal carbonyl clusters, such as [Co6(CO)i6]75), [Ru6C(CO)17]76) and [Co6(CO)i4]4- 77) in terms of localised M-CO... 

MgO-supported Rh6 and Irg clusters were also investigated as catalysts for ethene hydrogenation. Decarbonylation of hexanuclear metal carbonyl cluster precursors on MgO was used to prepare the catalysts. EXAFS data support octahedral clusters as the catalytically active species. Rh5/MgO is 1-2 orders of magnitude more active than Ir /MgO, as is the activity ratio for the conventionally prepared supported metals on silica. 

Many further examples could be added to those already cited to support the close relationship between carbonyl clusters and borane clusters, particularly for species based on an octahedron. These other clo80 octahedral clusters include anions such as Co0(CO)i6 (34), [Fe6(CO)ieC] - (35, 40), [Rhe(CO)i5l]- (6), [Nie(CO)i2] - (31), [Co4Ni2(CO)i4] (5), and [Rhi2(CO)8o], in which two Rhg octahedra are linked by a metal-metal bond and two bridging carbonyl groups (2). 

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