Trimerisation of the Cationic Fragments [(η-ring)M(Aa)]+ ((η-ring) M=(η5-C5Me5)Rh, (η5-C5Me5)Ir, (η6-p-MeC6H4iPr)Ru; Aa=α-amino acidate) with Chiral Self-Recognition: Synthesis, Characterisation, Solution Studies and Catalytic Reactions of the Trimers [{(η-ring)M(Aa)}3](BF4)3

Abstract

The formation of [{(η-ring)M(Aa)}3](BF4)3 trimers [(η-ring)M=(η5-C5Me5)Rh, (η5-C5Me5)Ir, (η6-p-MeC6H4iPr)Ru; Aa = α-amino acidate, one cation shown schematically] takes place by chiral self-recognition, the RMRMRM or SMSMSM trimers are equally configurated at the metal centres and are the only diastereomers detected. The equilibrium constant for the diastereomerisation process between both isomers depends on the solvent, amino acidate, and metal. The trimers catalyse the reduction of unsaturated aldehydes to unsaturated alcohols and the reduction of acetophenone to 2-phenylethanol with up to 75 % ee.