Optical resolution and absolute configuration of the chiral pentamethylcyclopentadienylrhenium carbonyl complex 5-C5Me5)Re(NO)(PPh3)(CO)>+BF4-

Article abstract of DOI:10.1016/0022-328X(90)85133-J

Reaction of racemic ester (η⁵-C5Me5)Re(NO)(PPh3)(CO2CH3) and (-)-(S)-α-(1-naphthyl)ethylamine gives amide (η⁵-C5Me5)Re(NO)(PPh3)(CONHCH(CH3)C10H7) (3) as a (SS)-/(RS)- diastereomer mixture.Crystallization gives the less soluble diastereomer (-)-(RS)-3 (77percent, <*> 98percent diastereomeric excess).Subsequent reaction with CF3CO2H and then NaBF4 gives carbonyl complex (-)-(R)-<(η⁵-C5Me5)Re(NO)(PPh3)(CO)>⁺BF4^- (91percent, <*> 99percent enantiomeric excess), which is in turn reduced (Li(C2H5)3BH/BH3 * THF) to methyl complex (-)-(R)-(η⁵-C5Me5)Re(NO)(PPh3)(CH3) (97percent).These serve as convenient precursors to a variety of other optically active complexes.Preparations of enantiomeric complexes, diastereomer (-)-(RR)-3, and recycling of the chiral α-(1-naphthyl)ethylamine auxilliary are also described.The structure and absolute configuration of (-)-(RS)-3 is verified crystallographically (orthorhombic, P2₁2₁2₁ (no. 19), a 12.348(4), b 13.198(5), c 22. 168(9) Angstroem, Z = 4).