Rhenium hydride

Finally, whilst rhenium hydride complexes have not been reported to hydrogenate alkenes, there are several reports of the dehydrogenation of alkanes in the presence of tBuCH=CH2 as an hydrogen acceptor (Scheme 6.14) [136-142]. For example, cycloalkanes are transformed catalytically into the corresponding cyclic alkene, which shows that, in principle, a Re-based catalyst could be designed. 

Rhenium halides, 21 699-700 Rhenium hydrides, 21 700 Rhenium imports, U.S., 21 688t Rhenium oxides, 21 699 Rhenium powder, 21 688, 689, 690, 693 specifications for, 21 694t Rhenium sulfides, 21 699... 

Reaction of the rhenium hydride complex ReH7(PR3)2 (where R = Ph or p-tol) with Au(PPh3)N03 has yielded the heteronuclear cluster compounds [Au5Re(H)4(PR3)2(PPh3)5](PF6)2 (148) in which the metal cores are based on edge-shared bitetrahedra with the rhenium atom at one of the two most-connected vertices. This is illustrated in Fig. 24. A... 

Treatment of an ethereal solution of lithiated bis(7r-cyclopenta-dienyl)rhenium hydride, (C5H4Li)oReH, with an excess of methyl iodide yields a rather unstable yellow compound of composition CisHmRe (125). The infrared and NMR spectra indicate that the complex is (methylcyclopentadiene)(cyclopentadienyl)dimethylrhenium for which the structure (48) has been deduced by X-ray analysis (5). The methyl-... 

On treating the compound (CsHslaReH, which has been mentioned earlier, with carbon monoxide at 90° and 250 atm it is possible to obtain the carbonyl (C6H5)2ReH(CO)2, which has neither acidic nor basic properties (8 ). It sublimes at 90-100°, melts at 111-112°, and is freely soluble in all the usual solvents such as benzene, ether, petroleum ether, and acetone. Unlike cyclopentadienyl rhenium hydride, it is stable in air. 

Synthesis and reactivity of hydrogen-rich uranium-rhenium compounds have been reported. The tris(cyclopenta-dienyl)uranium-rhenium hydride complexes [(CsFI4R)3UF[6Re(PPh3)2] (R=H, Buc, SiMe3) were prepared according to Scheme 87.175... 

Root and Beach also found that the as-deposited Re was not stable in air and moisture, because of the inclusion of rhenium hydride impurities. The quantity of hydride depends on the pH of... 

Figure 15. Phase transformation from amorphous rhenium hydride to crystalline Re following hydrogen annealing (T = 900-950°C, t = 1-1.5 h). Reprinted from Ref. 166, Copyright (1997) with permission from the Institute of Materials, Minerals and Mining.

The first known complex in this class, frans-bis(triethylphosphine)-platinum chlorohydride, was prepared by Chatt and co-workers (86). In the light of other hydrides known at that time, in particular the carbonyl hydrides of iron and cobalt and bis(7r-cyclopentadienyl)rhenium hydride, the great stability of this complex was quite unique. It rapidly became clear that tertiary phosphine ligands were markedly effective in stabilizing the metal-hydrogen bond, and ligands such as PhjP, EtjP, o-CaH PlVfe, ... 

The reverse transfer of a hydrogen from the metal to a 7r-cyclopentadieny] ring presumably occurs in the formation of 7r-cyclopentadienylcyclopen-tadienedicarbonylrhenium from bis-(7r-cyclopentadienyl)rhenium hydride and carbon monoxide 56, 107). Cationic complexes in this class, prepared by protonation reactions, are discussed in Section III,E. 

Bis(7r-cyclopentadienyl)rhenium hydride was the first hydride to be recognized for 20 years after the isolation of the carbonyl hydrides of iron and cobalt 22). Within the last few years the related hydrides of molybdenum, tungsten, and tantalum have been isolated 80, 99, 106) (Table VIII). 

Treatment of chloroform solutions of the dihydrides (XX) or the rhenium hydride (XIX) with chlorine or bromine results in both oxidation of the metal and replacement of the hydrogens (54). 

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