Optically Active Transition Metal Complexes. 130.1Synthesis, Crystal Structures, and Catalytic Properties of Chiral-at-Metal (η6-Arene)ruthenium(II) and (η6-Arene)osmium(II) Half-Sandwich Complexes. Crystallization of Pure Diastereomers versus Diastereomer Mixtures in a 1:1 Ratio

Condensation of a number of optically active amines and α-amino acid esters with salicylaldehyde gave the chiral compounds HLL*-1 − HLL*-8 . A series of diastereomeric complexes of the type ( R M, S C )- and ( S M, S C )-[(η 6 -arene)M(LL*)X] ( 1 − 14: M = Ru, Os; X = Cl, I), differing only in the metal configuration, were formed by reaction of [(η 6 -arene)MCl 2 ] 2 with these compounds in the presence of base and by halogen exchange. Five of the complexes were characterized by X-ray structure analyses. Three cases showed the structural peculiarity that the single crystals contained the R M, S C and S M, S C diastereomers with opposite configurations at the metal centers in a 1:1 ratio, whereas two cases crystallized as pure R M, S C diastereomers. Two complexes, the ligands of which (the salicylaldiminates of methyl phenylalaninate and methyl phenylglycinate) had racemized during the synthesis, crystallized as racemates R Ru, S C / S Ru, R C . Complexes 1 − 14 were tested as catalysts in the enantioselective isomerization of 2- n -butyl-4,7-dihydro-1,3-dioxepin to give 2- n -butyl-4,5-dihydro-1,3-dioxepin. Enantioselectivities up to 64% ee were achieved.