Osmium carbonyl clusters structures

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],... 

Fig. 4.11 The metal cores of a series of structurally characterized tetrahedral osmium carbonyl clusters (I [H2Os4(CO)12]2 II [Os10C(CO)24]2 III [Os20(CO)40]2 from ref. 173 reproduced with permission of the Royal Society of Chemistry)...

Triply bridging thiolate complexes of osmium carbonyl clusters are less common than for iron. The [Os3(CO)9(//-H)(/i3-SR)] complexes (R = Me, Et) are unstable but can be conveniently trapped as ethylene adducts subsequent regeneration of the parent complexes is facile. The X-ray structure of one such 7r-coordinated ethylene adduct, [Os3(CO)9(//-C2H4)(/r-H)(//3-SMe)], has been reported. " Very few examples of Ru clusters with 3-SR coordination (R = Bu, Pr ) have been reported in the literature. ... 

Nine neutral osmium carbonyl clusters, Os j(CO)3,., are known to us to have been structurally characterized, only one of which, Os3(CO)i2, has been the subject of a... 

Figure 6. The structures of the osmium carbonyl clusters discussed in this work , Os(CO)4 , Os(CO)3 , Os(CO)2 , Os(CO). Hydride and bridging carbonyl ligands are drawn explicitly.

A direct comparison of the computed DOS curves with the UPS spectrum of a cluster has no theoretical justification since the former does not take into account orbital relaxation and many-body effects. However, this is not too serious a limitation given the relatively small relaxation and the qualitative nature of the comparison. With this in mind, the DOS curves and the UPS spectra of osmium carbonyl clusters have been compared. [261, 296] The positions of the computed ener levels correlate well with the structure of the UPS spectrum (Fig. 2-32). 

R.D. Adams, I.T. Horvath - The Unusual Structures, Bonding, and Reactivity of Some Sulfido-Bridged Tungsten-Osmium Carbonyl Cluster Compounds,... 

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