Osmium carbonyl clusters reactions

Osmium forms stronger metal-metal bonds than either iron or ruthenium consequently, there are a large number of osmium carbonyl clusters see Cluster) and these complexes have a large body of reaction chemistry. The triosmium cluster are prepared from Os3(CO)i2. Most are diamagnetic... 

A series of osmium carbonyl complexes have been prepared by the reaction of OsO-with CO or decomposition of Os3(CO)i2 [226] and a mononuclear homoleptic osmium carbonyl complex, Os(CO)5, is also known. It is a volatile, colorless liquid and is the most robust M(CO)5 type complex of the iron triad against both oxidation and heat but it gradually loses CO to form Os3(CO)i2. Multinuclear osmium carbonyl clusters such as Os3(CO),2, Os5(CO)i6, Os5(CO)i9, Os6(CO)ig, 087(00)2, and OsgfCO).. have also been reported [227]. In this section, several carbonyl complexes based on Os3(CO)j2are described. 

Substituted carbonyl clusters react with halogens in much the same way as their parent carbonyls. The final products of the reaction of halogens with Ru3(CO)9(PPh3)3 are the dimers [Ph3PRu(CO)2X2]2, as detected by Piacenti and co-workers (325, 326), but the initial products are the mononuclear Ph3PRu(CO)3X2 which dimerize with loss of CO just as the Ru(CO)4X2 compounds did (212). No trinuclear products were detected. The corresponding trisubstituted osmium carbonyl cluster... 

The Surface of Inorganic Oxides an Unusual Reaction Medium for the High-yield and Selective Synthesis of Various Osmium Carbonyl Clusters... 

Surface-mediated syntheses of anionic osmium carbonyl clusters from neutral complexes, clusters, or salts require a surface of adequate basicity as the reaction medium. This has been achieved by two different approaches. The first is the use of an intrinsically strongly basic surface such as magnesia. The basicity of this surface can be easily varied by adjusting the temperature of the treatment. Increasing the temperature leads to gradual decarbonation and dehydroxylation of the surface with creation of very basic centers, and therefore to increased surface basicity.l Similar thermal behavior is observed with the less basic alumina surface.t l... 

The use of the surface of inorganic oxides as reaction media enables selective and high-yield syntheses of a variety of neutral and anionic osmium carbonyl clusters starting from simple and readily available materials. The procedures are simple and straightforward. Because the use of a solid as a reaction medium is not limited, as in solution, by boiling points, it is possible to work at atmospheric pressure even at relatively high temperatures. 

Numerous palladium-osmium clusters have been prepared and characterized through the reaction of osmium carbonyl clusters with palladium(O) and palladium(ii) complexes. The simplest of these is probably (bipy)Pd 20s3(G0)i2, which is prepared from Os3(/i-H)2(GO)io and Pd(OAc)2(bipy). This cluster is made up of a triangular arrangement of Os3(GO)s, with two (/x-GO)2Pd(bipy) units attached to two of the osmium atoms (43, terminal osmium carbonyls omitted for clarity). Each palladium atom has one symmetrically bound and one semibridging carbonyl ligand associated with it (Pd-GO= 1.98(2) and 2.34(2) A). 

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] ... 

Fig. 2.56. Reduction reactions of osmium carbonyl clusters [John GR, Johnson BFG, Lewis J (1979) J. Organomet. Chem. 186 C69 Vargas MD, Nicholls JN (1986) Adv. Inorg. Chem. Radio Chem 30 123]...

As befits current interest, the largest number of reviews centre on metal carbonyl cluster compounds. General topics covered included electron transfer reactions, ligand and cluster transformations, and the chemistry of metal clusters containing nitrosyl and nitrido ligands.More specific topics reviewed include sulphi do-osmium carbonyl cluster compounds,and homonuclear platinum clusters.The preparations of [Nb(C0)6] [M2(CO)io(m-H)]" (M = Cr or W), Mn2(C0)aX2 and Re C0)sX (X = Cl, Br or I) are described in Volume 23 of Inorganic Syntheses. ... 

The chemistry of osmium carbonyl clusters in basic Y zeolite (NaY treated with NaN3) in CO hydrogenation reactions was studied by Zhou etal. [222]. The possible formation of metal clusters in the course of CO-hH2 reactions was mentioned. 

The reaction with [Mn(CO)5]2 or [Co(CO)4]2 also led to mixed-metal clusters.962,963 Osmium-palladium mixed-metal carbonyl clusters were made using the unsaturated cluster [Os3(CO)io(/r-H)2] and the carbido cluster [Os5(/U5-C)(CO)15].964 970 Treatment of [Os3(CO)10Gu-H)2] with [Pd2(/u-dppm)2Cl2] afforded the novel high-nuclearity osmium-palladium mixed-metal carbonyl clusters [Os5Pd6(CO)13( -CO)5(/u-H)2(/u-dppm)2], [Os5Pd6(CO)13(//-CO)6(/u-dppm)2], and... 

The formation of carbido-carbonyl cluster compounds with ruthenium and osmium appears to be common in pyrolysis reactions the basic reaction may be viewed as the transformation of the coordinated carbon monoxide to carbide and carbon dioxide. Small variations in... 

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