Osmium carbonyl clusters dianion

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],... 

By using milder nucleophiles than OH such as nitriles and halides, it is also possible to reduce high nuclearity osmium carbonyl clusters to the corresponding dianions. Thus, for instance, the reaction of Os6(CO)is with different nitriles or with iodide leads to the dianion [Os6(CO)i8] ... 

Metal carbonyl cluster compounds which contain three ruthenium or three osmium atoms in the cluster core are common.1 Potentially useful reagents for syntheses of these compounds are the triruthenium and triosmium dianions [M3(CO)h]2 (M = Ru, Os).2 Therefore, it is desirable to develop good synthetic routes to obtain [M3(CO)11]2- (M = Ru, Os) of high purity in high yields. A method that is particularly useful for generating [M3(CO)n]2 (M = Ru, Os) is the designed stoichiometric reduction of M3(CO)12 (M = Ru, Os) using an electron carrier such as potassium-benzophenone.3... 

The early chemistry of hexanuclear carbonyl clusters, including those of ruthenium and osmium, has been reviewed.The hexaruthenium dianion [RuslCOlis] is prepared inside NaX-zeolite cages in 80-90% yields by treatment of [Ru(NH3)6] /NaX with CO and H2. Oxidation of the supported dianion results in cluster degradation to mononuclear ruthenium products, a process that is reversible on re-exposure to CO/H2. A redetermination of the crystal structure of Os6(CO)i8, as its chloroform solvate, confirms the bicapped tetrahedral metal core seen with the unsolvated cluster. 

The parent heptanudear osmium cluster, [Os7(CO)2i], is prepared from the pyrolysis of [Os3(CO)i2]. The crystal structure confirms that the metal framework is a capped octahedron consistent with electron count of 98 e and the presence of seven skeletal electron pairs.The neutral carbonyl can be readily reduced to the dianion [Os7(CO)2o] with K/Ph2CO, and an X-ray analysis shows that the capped octahedral metal framework is retained (Fig. The reaction of this dianion... 

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