Cyclopentadienyl rhodium tris

Reaction of the cyclopentadienyl rhodium and iridium tris(acetone) complexes with indole leads to the species 118 (M = Rh, Ir) [77JCS(D)1654 79JCS(D)1531]. None of these compounds deprotonates easily in acetone, but the iridium complex loses a proton in reaction with bases (Na2C03 in water, r-BuOK in acetone) to form the ri -indolyl complex 119. This reaction is easily reversed in the presence of small amounts of trifluoroacetic acid. 

From the bulky (l,2,4-triisopropyl-3,5-dimethylcyclopentadienyl)rhodiumbis(ethylene) and (l,2,4-tri-/i / -butyl-cyclopentadienyl)rhodiumbis(ethylene) the corresponding (cyclopentadienyl)rhodium carbonyl dimers 67 and 68 were obtained. 

O-Methylation of mandelic acid leads to the enantiomers of a-methoxy-M-phcnylacetic acid (10), which are also commercially available. This methylation without noticeable racemiza-tion was achieved with diazomethane, using aluminum tris(tert-butanoate) as catalyst8. Alternatively, dimethyl sulfate/ sodium hydroxide has been used15, as described in detail for the racemic compound10. The acids have been used for the construction of quite sophisticated chiral auxiliaries, e.g., a rhodium cyclopentadienyl complex (Section 7.2.2.), and for chiral dienes applied in both normal and inverse Diels-Alder reactions (Section D.1.6.1.1.1.). Chiral dienes, e.g., 1, for normal Diels -Alder reactions were prepared by pyrolysis (460 C) of a tricyclic precursor cstcrified with (S)-O-methylmandeloyl chloride or with the free acid and dicyclohexylcarbodiimide/4-dimethylaminopyridine11 -13. 

Aris et al. (9) examined cyclopentadienyl (propene) irondicarbonyl tri-fluoroacetate and dipropenerhodiumacetylacetonate. In the iron complex the olefinic resonances are shifted upheld by approximately 60 ppm (methylene carbon) and approximately 50 ppm (methine carbon). These shifts indicated, in the authors view, that there was extensive backbonding. For the rhodium complex, the methylene and methine resonances are also shifted upheld upon coordination, but the difference between the upheld shifts (J C(l)-d C(2)) is smaller. 

OPjRhCssH, Rhodium(I), carbonyl-hydridotris(triphenylphosphine)-, 28 82 OSjCH, Dithiocarbonic acid, 27 287 OSiC Hi2, Silane, methoxytrimethyl-, 26 44 OSmCisHjj, Samarium(III), tris(>/ -cyclopentadienyl) (tetrahydrofuran)-, 26 21... 

Cl 7H24F12NP2Rh, T -Pentamethylcyclopentadienyl-(6-methylimino-1 -5-rj-cyclohexadienyl)rhodium hexafluorophosphate, 46B, 882 ClaHioClCoFe208Sn, Chloro-bis(T -cyclopentadienyldicarbonyliron)-(tetracarbonylcobalt)tin(IV), 46B, 883 Cl 8 1oFe20eRh2, Tri-M carbonyl-pentacarbonylbis-(7r-cyclopentadienyl-rhodio)di-iron(Rh-Rh)(Fe-Fe)(4Rh-Fe), 37B, 458 ClaHi0O8RU3, Tetracarbonylbis[dicarbonyl-(T -cyclopentadienyl)-... 

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