Rhenium complexes cyclopentadiene

An interesting property of some cyclopentadiene- and cyclohexadienyl-metal complexes is the occurence of unusually broad, low frequency bands (2700 cm" ) which arise from a C—H stretch of the methylene carbon. The crystal structure of the rhenium complex, 7.21, which also has an unusually low C—H stretch, shows that the C—hydrogen is in the exoposition. It is reasonable to suppose that the unusual C—H stretches in the related complexes also arise from the C—H, bond. It has been suggested that the C—frequency is lowered as a result of direct interaction between the metal and the methylene carbon. 

The formation of the hydrides may proceed via bis(jr-cyclopentadienyl)-metal halide complexes, since compounds such as (ir-CeH ReCU+CI-and (t-CjHOjWCU are known and are readily reduced to the neutral hydrides on treatment with lithium aluminum hydride 64) (Eq. 5). Treatment of technetium tetrachloride with sodium cyclopentadiene does not give a hydride analogous to that of rhenium. Molecular weight determina-... 

Metal carbonyl complexes of steroids have been synthesized by the groups of Jo-hannsen and Katzenellenbogen (Arterburn et al. 2003 Bigott et al. 2005 Luyt et al. 2003 Wust et al. 1998, 1999). Various 17j -progesterone and 7a-estradiole dithioether and cyclopentadiene complexes of technetium/rhenium(I) tricarbonyl have been pre-... 

The Gladysz group have again published widely in rhenium nitro and cyclopentadiene chemistry. The diolate compounds 10 ami 11 were prqiared from the reaction of Cp Re with NBD at > 9(fC. This is a reversible process. The coupling of an ethynyl ligand in the complex (Cp )Re(NO)(PPh3)(C CH) with Cu(OAc>2 leads to the dimeric complex. 

Two distinct observations are made with respect to the hydrogenation of olefin 7i-complexes with catalysts such as raney nickel. When the olefin is firmly bound to a metal, complete catalytic hydrogenation is prohibited. Thus 7i-cyclopentadienylcobalt cyclooctatetraene (6-22), 7r-cyclopentadienyl tt-cyclopentadiene rhenium dicarbonyl (6-23), and Tr-cycloheptatriene iron tricarbonyl (6-24), each of which contains at least one uncomplexed double bond, readily undergo hydrogenation of the uncomplexed bonds only. The metal-olefin bond is preserved in each case. 

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