HIGHLY STEREOSELECTIVE FORMATION OF CP-ASTERISK-IRCL COMPLEXES OF N,N-DIMETHYLAMINO ACIDS

N,N-Dimethylamino acids serve as (N, O)-chelating monoanionic ligands to the prochiral fragment CpIrCl. A series of four such complexes and one Rh analog all were formed with diastereoselectivity of greater th an or equal to 50: less than or equal to 1. The structure of the valin e complex 5d (C17H29ClIrNO2) was analyzed at 298 K, from which a cis-a rrangement of Cp and valine side chain (i-Pr) was revealed. Solution NMR studies of 5d, aided by an unusual zero coupling between the two m ethine protons of the amino acid, showed that the structures in soluti on and the solid were very similar. The preference for the cis-oriente d Cp and amino acid side chain in 5 is attributed to a maximum number of gauche interactions in the metallacycle and its substituents, espe cially pronounced for N,N-disubstituted amino acids.