Molybdenum, hydride compound

In the Li-Rh system LiRh is prepared from rhodium metal foil and liq Li in a 25 at% excess of the 1 1 molar ratio. The mixture is heated in an iron crucible to 750-880°C in Ar. The direct reaction of the elements in a molybdenum crucible at 800°C for 7 d produces LiRh. Identical methods produce Lilr and Lilrj with which the rhodium compounds are isostructural . The reaction of Rh metal with LiH at 600°C gives the ternary hydrides Li4RhH4 and Li4RhH5. 

Because of the unusual nature of this molecule—it is the first molecular zinc(i) compound—it was thoroughly chemically and structurally characterized. Low-temperature X-ray structures with both molybdenum and copper radiation led to identical results (Figure 78). The structure of (r -CsMes n-Zn -CsMes) consists of two eclipsed ( 75-C5Me5)Zn units connected by a direct zinc-zinc (2.305(3) A) bond, which is substantially shorter than the sum of the covalent radii of two zinc atoms (2.50 A). The presence of bridging hydrides was discounted by the high resolution mass spectral data and by protonolysis. 

A sulfuric acid solution of the oxide (25-75% solution) can be reduced with tin, copper, zinc, and other reducing agents forming a blue solution of molybdenum blue which are hydrous oxides of non-stoichiometric compositions (see Molybdenum Blue). Reduction with atomic hydrogen under carefully controlled conditions yields colloidal dispersion of compounds that have probable compositions Mo204(OH)2 and Mo40io(OH)2. Reduction with lithium aluminum hydride yields a red compound of probable composition MosOtIOEOs. Molybdenum(Vl) oxide suspension in water also can be reduced to molybdenum blue by hydriodic acid, hydrazine, sulfur dioxide, and other reductants. 

Phillips and Timms [599] described a less general method. They converted germanium and silicon in alloys into hydrides and further into chlorides by contact with gold trichloride. They performed GC on a column packed with 13% of silicone 702 on Celite with the use of a gas-density balance for detection. Juvet and Fischer [600] developed a special reactor coupled directly to the chromatographic column, in which they fluorinated metals in alloys, carbides, oxides, sulphides and salts. In these samples, they determined quantitatively uranium, sulphur, selenium, technetium, tungsten, molybdenum, rhenium, silicon, boron, osmium, vanadium, iridium and platinum as fluorides. They performed the analysis on a PTFE column packed with 15% of Kel-F oil No. 10 on Chromosorb T. Prior to analysis the column was conditioned with fluorine and chlorine trifluoride in order to remove moisture and reactive organic compounds. The thermal conductivity detector was equipped with nickel-coated filaments resistant to corrosion with metal fluorides. Fig. 5.34 illustrates the analysis of tungsten, rhenium and osmium fluorides by this method. 

Apart from the di- and oligoolefm iron tricarbonyl complexes, which nowadays are frequently used in organic synthesis [71, 72], the chemistry of the readily accessible cyclohepatriene chromium and molybdenum tricarbonyls 2 and 3 was the focus of intense research efforts as well. Only a few months after the synthesis of 2 and 3 was published [58,59], both Hyp Dauben and Peter Pauson reported that these compounds react with triphenylmethyl tetrafluoro-borate in methylene chloride to give the tropylium complexes 4 and 5 in excellent yield (Scheme 7.1) [73, 74]. Later this method of hydride abstraction was also used for the preparation of the tropylium cation itself and subsequently led to the generation of several cationic rc-complexes of iron, manganese and cobalt [71, 72], The reactions of the cations of 4 and 5 with nucleophilic... 

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