Inorganic asymmetric synthesis: Asymmetric synthesis of a two-bladed propeller, octahedral metal complex

A C-2 hexadentate, in which two pyridine-2-aldehyde 2'-pyridylhydrazone ( PAPHY) groups are linked to a chiral auxiliary derived from (R,R)-tartaric acid, (R,R)-1, reacts with iron(II) benzenesulfonate to give the two-bladed propeller, octahedral complex (P-Fe)-[Fe{(R,R)-1}](PhSO3)(2) with complete diastereoselectivity, as determined by H-1 NMR spectroscopy and X-ray crystallography. Saponification of the ester linkages and deprotonation of the hydrazone-NH groups in the configurationally pure diastereomer affords the complex (P-Fe)-[Fe(5-HOCH(2)PAPY)(2)] with 85% retention of configuration at the iron stereocenter, as determined by reprotonation of the neutral complex with enantiomerically pure (aR)-binaphthyl phosphoric acid and analysis of the H-1 NMR spectrum of the mixture of diastereomeric salts produced. This is the first asymmetric synthesis of a two-bladed propeller, octahedral metal complex by the classical organic methodology of chiral auxiliary-directed, asymmetric synthesis.