Diastereoselective Substitution of PR3 for CO in Carbohydrato‐ and Menthyloxycarbene Complexes of Manganese – Synthesis of Chiral‐at‐metal Carbene and Carbyne Complexes

Abstract

AbstractThe substitution of PR3 (R = C6H4CH3‐p, C6H4Cl‐p, C6H11,OCH3) for a CO ligand in chiral carbohydratocarbene complexes [(η5‐C5H5)(CO)2MnC(OR*)Ph] [OR* = α‐ (1α) and β‐mannofuranosyl (1β), (–)‐menthyloxy (9)] proceeds diastereoselectively. The diastereoselectivity depends on PR3 and on the OR* substituent and ranges from 12% de (R = OCH3) to 80% (R = C6H4CH3‐p). In contrast, the reaction of 1β with P(OPh)3 is non‐selective. The diastereoselectivity generally increases with increasing nucleophilicity of PR3 and decreases in the series 1β > 1α > 9. The highest diastereoselectivity was observed in the reaction of 1β with P(C6H4CH3‐p)3. Predominantly, the isomer with the (S) configuration at the metal [(S Mn)‐2β] was formed which could be separated from the diastereomeric mixture by chromatography and be obtained in a pure form. Subsequent reaction of (SMn)‐2β with BF3 afforded the carbyne‐manganese complex (SMn)‐[(η5‐C5H5){P(C6H4CH3‐p)3}(CO)MnCPh]BF4.