PREPARATION OF CHIRAL TRICARBONYL-(MU(6)-ARENE)CHROMIUM(0) COMPLEXES DERIVED FROM (S)-2-INDOLINECARBOXYLIC ACID

The title diastereomeric mixture of (S,S)- and (R,S)-tricarbonyl[methy l lsilyl-(S)-eta6-indolene-2-carboxylate]chromium(0) was prepared by f irst converting (S)-2-indolinecarboxylic acid to N-tert-butyldimethyls ilyl-(S)-2-indolinecarboxylic acid methyl ester. The enantiomerically pure ester was subjected to complexation conditions using triammine(tr icarbonyl)chromium and hexacarbonylchromium to yield a 1:1 diastereome ric mixture of the corresponding tricarbonyl(eta6-arene)chromium(0) co mplexes. Chromatographic separation of the two diastereomers which res ult from addition of the tricarbonyl fragment to either face of the ar ene portion of the ester was effected. The bonding distances for the t wo diastereomers are very similar, but they have significantly differe nt molecular conformations. These differences appear to result primari ly from differences in the steric interaction between the acid ester g roup and the tricarbonylchromium fragment.