Cluster hydrides, synthesis

Methylthio)thiophene, with trinuclear Os clusters, 6, 744 Methyltin hydride, synthesis, 3, 844 Methyltitanation, alkynes, 10, 256 Methylzirconocene ester enolates, preparation, 4, 923 Methylzirconocene pyrazolyl compounds, preparation,... 

Asymmetric Synthesis by Homogeneous Catalysis Carbonylation Processes by Homogeneous Catalysis Coordination Organometalhc Chemistry Principles Electronic Stmcture of Clusters Hydride Complexes of the Transition Metals Hydrides Sohd State Transition Metal Complexes Organic Synthesis using Transition Metal Complexes Containing 7t-Bonded Ligands Oxidation... 

The reaction of metal carbonyl complexes with carbonyl anions is a widely used technique for synthesis of mixed-metal clusters. This reaction is also termed reductive condensation or redox condensation. The metal carbonyl anion may be generated in situ or may be separately isolated. The mixed-metal product is usually an anion protonation can be used to generate a neutral cluster hydride. 

There are numerous triangular metal complexes containing hydrogen. Structural features of hydride metal clusters will be separately described in Chapter 3. The study of cluster hydrides is of considerable interest since, as it will be discussed later in this Chapter (Sect. 2.6), they are intimately associated with important catalytic processes e.g. Fischer Troppch processes for ammonia and methane synthesis. 

In some instances, particularly when the ruthenium trichloride sample contains more than the usual amount of water (this may occur, e.g., with old samples or on long exposure to moist air), the isolated product may be a mixture of Ru3(CO)12 and Ru4(/ -H)4(CO)12 (as indicated by the IR v(CO) spectrum). In such cases, depending upon the final product required (a) the product may be used directly as in the synthesis of Ru4( -H)4(CO)12 described below, when conversion to the cluster carbonyl hydride is completed by reaction with H2 or (b) treatment of the product with CO for 1 h while suspended in refluxing octane, using the apparatus depicted in Fig. 1, results in conversion of any Ru4(/i-H)4(CO)12 to Ru3(CO)12. 

Under mild conditions, hydroformylation of olefins with rhodium carbonyl complexes selectively produces aldehydes. A one-step synthesis of oxo alcohols is possible using monomeric or polymeric amines, such as dimethylbenzylamine or anion exchange resin analog to hydrogenate the aldehyde. The rate of aldehyde hydrogenation passes through a maximum as amine basicity and concentration increase. IR data of the reaction reveal that anionic rhodium carbonyl clusters, normally absent, are formed on addition of amine. Aldehyde hydrogenation is attributed to enhanced hydridic character of a Rh-H intermediate via amine coordination to rhodium. 

In the report that described the synthesis of 108 (777), Whitmire also observed that the reaction between NaBi03 and methanolic [Fe(CO)s] in the presence of hydroxide afforded the trianionic species [Bi Fe(CO)4 4]3, 110, which was subsequently characterized by X-ray crystallography (775). Cluster 110 contains a central bismuth atom tetrahedrally coordinated by four Fe(CO)4 fragments and is isoelectronic with the anionic tetracobalt-indium complex, 27, and the neutral tetracobalt-germanium, - tin, and -lead complexes, 68, 71, and 72. Oxidation of 110 affords 108 (777), while acidification (772) yields the hydride-containing cluster [BiFe3(CO)9(/i-H)3], 111, which also contains a tetrahedral BiFe3 core. Johnson and Lewis (114) have... 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

An unsaturated compound in the course of its isomerization in magnesium-containing films performs two functions (i) it forms a catalyst when the Mg4 cluster is inserted into the activated C-H bond, and (ii) it acts as a reaction substrate. The stages of the synthesis of the catalyst and isomerization can be separated. For example, anthracenyltetramagnesium hydride can be preliminarily obtained in anthracene-magnesium films, and then it can be used as a catalyst. The introduction of this cluster compound into a solution of allylbenzene or methylindene at room temperature ensures high yields of multiple bond migration products. 

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