METAL-COMPLEXES OF BIOLOGICALLY IMPORTANT LIGANDS .64. PENTAMETHYLCYCLOPENTADIENYL RHODIUM(III) COMPLEXES WITH ALPHA-AMINO-ACID DERIVATIVES AS BRIDGING LIGANDS AND WITH SEVERAL CHIRAL METAL CENTERS - SYNTHESIS AND STRUCTURE OF [CP-ASTERISK-RH(MU-L-PHENYLALANINATO)]3(BF4)3 AND [CP-ASTERISK-RH(MU-NHCOCH2NCO2CH2PH)]2

Elimination of chloride from Cp*Rh(L-PheO)Cl with AgBF4 leads to the trinuclear complex [Cp*Rh(mu-L-PheO)]33+(BF4-)3 (2), in which the amino acidate acts both as an (N, O)-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 (R(Rh)R(Rh)R(Rh) and S(Rh)S(Rh)S(Rh)) are formed. Reaction of [Cp*RhCl2]2 with carbobenzoxy glycine amide in the presence of base gives the dimeric complex [Cp*Rh(mu-NHCOCH2NCO2CH2Ph)]2 (3). X-ray diffraction showed that the two rhodium atoms with R(Rh)S(Rh) 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 N,N-dimethylglycine ethylester in CD3OD.