Synthesis of Configurationally Stable, Optically Active Organocobalt Compounds

Abstract

The transmetalation reaction between a series of ortho-lithiated tertiary amine derivatives (N∧C−Li) and [(η5-C5H5)CoI2]2 affords a series of cobaltacyclic compounds of the general form (η5-C5H5)Co(C∧N)I, in which the cobalt center is in a pseudotetrahedral environment. With optically active lithiated compounds, such as those obtained from (R)- or (S)-1-(dimethylamino)-1-phenylethane, the reaction forms a mixture of two diastereoisomers (RC,RCo)-12a, (RC,SCo)-12a‘ and (SC,RCo)-12b, (SC,SCo)-12b‘, respectively, of which the isomers 12a and 12b‘ are predominant, as they are formed with a de of 90%. 1H NMR studies indicate that the compounds are configurationally stable at the cobalt center. Reaction of these species with neutral ligands such as phosphines, phosphites, or isocyanides led to the formation of cationic complexes via substitution of the iodide ligand, this reaction occurring mainly with retention of configuration for the optically active species.