Rhenium dimer

Two intermediate oxidation-state rhenium dimers containing the Ref moiety have been structurally characterized with metal-metal separations of... 

BM) forms with a quantum yield of 0.017 0.005 when Re2Cl " is irradiated at 313 nm. Cleavage of the quadruple bond to form ReCl4(CH3CN)2 is followed by rapid conversion to the neutral monomer by means of acetonitrile replacement of chloride. No reaction occurs in the absence of irradiation at reflux, and the 88 excited state is not responsible for the observed photochemistry, since 632.8 nm radiation does not lead to cleavage of the rhenium dimer (135). Flash-photolysis studies suggest that the dominant photochemical process involves internal conversion to a transient 65 excited... 

NHt MojClg-NUtCFHjO (35) reveal metal-metal bond lengths that are essentially equal [2.148(2) and 2.150(5) A, respectively], while [Li(Et20)]2-Re2(CH3)8 (80) and [(C4H,)4N]2Re2Cl8 (77) differ by almost 0.05 A [2.178(1) and 2.224(1) A, respectively]. The much larger shift observed for the 5 - 5 transition in the rhenium dimers is certainly a reflection of this increased metal-metal overlap. 

The conclusion that variations in the coupling of vibrational modes in these dimers is not responsible for the entire frequency shift is an important point in that it justifies the search for a chemical rationale of the bonding differences in Mo2Xf and Mo2(02CR)4. The authors suggest that 6 bonds may make an important bonding contribution in rhenium dimers and molybdenum carboxylates to account for Fmm near 4.5 mdyne A-1. Furthermore, it is proposed that such a 6 component would probably not contribute significantly in the molybdenum halides where is near 3.5 mdyne A"1, possibly... 

Spectral characterization of the phosphine-substituted rhenium dimers included electronic spectra and infrared data (124). Detailed assignments of electronic absorption bands were not proposed by the authors, but characteristic structure-spectra features were identified. For the Re2+ unit the lowest energy absorption was in the range of 695- 760 nm, similar to results in previous Ref+... 

Confirmation of the bridging behavior of dppm in rhenium dimer chemistry has been obtained by x-ray analysis of the minor product of the reaction of dppm with Re2Cll in acetone (111). The brown, air-stable solid recrystallized from toluene and having the stoichiometry Re2 Gs (dppm)j 2C6H5CH3 has the eclipsed structure with two bridging dppm ligands and one terminal chloride as shown in Fig. 17. This dimer thus differs from the Re2Cls... 

Fujita et al. (89-91) reported that 16 is produced by irradiating the rhenium dimer complex, (COsldmblRe—Re(dmb)(CO)3, in THF under a CO2 atmosphere. This reaction has been reported to proceed by the reaction between CO2 and the 17-electron species [Re(dmb)(CO)3] generated by light-induced homolysis of the dimer (see Section III.B for homolysis of the Re—Re bond). The photoreaction of (CO)3(dmb)Re—CO2—Re(dmb)(CO)3 with CO2 quantitatively 5nelded CO and C03. ... 

Formation of Heavy Transition Metal Group VII Metal-Metal Bonds 87 9.2.10.1. Synthesis of Dimeric Technetium and Rhenium Compounds 9.2.10.1.2. Syntheses of Rhenium Dimers Without Re Unit. 

An alternative procedure involves the photochemical cleavage of the rhenium-rhenium bond in dirhenium decacarbonyl in the presence of a chlorocarbon solvent.21,22 This method suffers from contamination by the tetracarbonylchloro-rhenium dimer, which forms in large quantities during photolysis.21,22 To prevent formation of dimer, the photolysis is performed under an atmosphere of carbon monoxide. The yield of ReCl(CO)5 is essentially quantitative using this procedure. 

ClsHi6N203Sn, Diphenyltin glycylglycinate, 43B, 926 Cl5H1gNioOigPb, Aquobis(purpurato)lead(II) trihydrate, 43B, 511 ClgHisGe20ioRe2 f Dimethylgermyl-acetyl(tetracarbonyl)rhenium dimer, 40B, 686... 

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