Metal complexes of biologically important ligands. Part LXIV. Pentamethylcyclopentadienyl-rhodium(III) complexes with α-amino acid derivatives as bridging ligands and with several chiral metal centers: synthesis and structure of [Cp*Rh(μ-L-phenylalaninato)]3(BF4)3 and [Cp*Rh(μ-NHCOCH2NCO2CH2Ph)]2
✍ Scribed by Roland Krämer; Kurt Polborn; Christian Robl; Wolfgang Beck
- Publisher
- Elsevier Science
- Year
- 1992
- Tongue
- English
- Weight
- 606 KB
- Volume
- 198-200
- Category
- Article
- ISSN
- 0020-1693
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✦ Synopsis
Elimination
of chloride from Cp*Rh(L-PheO)Cl with AgBF, leads to the trinuclear complex [Cp*Rh(p-L-Phe0)],3+(BF4-)3 (Z), in which the amino acidate acts both as an (N, 0)-chelating and as a carboxylate bridging ligand according to the X-ray structural determination. Trimerization of [Cp*Rh(PheO)]+ occurs with chiral self recognition, i.e. in solution and in the crystal only diastereomers with the same configuration at the three chiral rhodium atoms (RRhRRhRRh and SRhSRhSru,) are formed. Reaction of [Cp*RhCl& with carbobenzoxy glycine amide in the presence of base gives the dimeric complex [Cp*Rh(p-NHCOCH,NCo,CH,Ph)l, (3). X-ray diffraction showed that the two rhodium atoms with RRhSRh configuration are bridged by the deprotonated glycine amide N atom. Complexes 2 and 3 may be of interest as chiral catalysts; they catalyze the ester exchange of NJVdimethylglycine ethylester in CD,OD. **For Part LXIII see ref. 10. 'Authors who carried out crystal structure determination. "Author to whom correspondence should be addressed. recorded on the following instruments: Nicolet ZDX 5 (IR), Jeol GSX 270 (NMR).