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Menthyl-Functionalized Chiral Nonracemic Monoindenyl Complexes of Rhodium, Iridium, Cobalt, and Molybdenum

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journal contribution
posted on 01.05.2001, 00:00 by Herbert Schumann, Oleg Stenzel, Sebastian Dechert, Frank Girgsdies, Ronald L. Halterman
Optically active complexes of Rh, Ir, Co, and Mo containing the chiral, menthyl-substituted indenyl ligands (−)-3-menthyl-4,7-dimethylindene, (−)-4,7-diisopropyl-3-menthylindene, and (+)-3-neomenthylindene are described. Metathetic reaction of the chiral main group metal salts of these indenyl systems with the appropriate starting materials of Rh and Ir yielded the complexes (−)-(pR)/(pS)-(1-menthyl-4,7-dimethylindenyl)Rh(COD) (7a/b), (pR)/(pS)-(1-menthyl-4,7-diisopropylindenyl)Rh(COD) (8a/b), (+)-(pR)/(pS)-(1-neomenthylindenyl)Rh(COD) (9a/b), (pR)/(pS)-(1-menthyl-4,7-dimethylindenyl)Rh(C2H4)2 (10a/b), (pR)/(pS)-(1-menthyl-4,7-dimethylindenyl)Rh(CO)2 (11a/b), (pR)/(pS)-(1-menthyl-4,7-dimethylindenyl)Rh(CO)(PPh3) (12a/b), (pR)/(pS)-(1-menthyl-4,7-dimethylindenyl)Rh(CO)(PPh2CH2CH2Si(OCH3)3) (13a/b), and (−)-(pR)/(pS)-(1-menthyl-4,7-dimethylindenyl)Ir(COD) (14a/b). CoCl2(dppe) reacts with (−)-(1-menthyl-4,7-dimethylindenyl)lithium (1), yielding (pR)/(pS)-(1-menthyl-4,7-dimethylindenyl)Co(dppe) (15a/b). Li[(pR)/(pS)-(1-menthyl-4,7-dimethylindenyl)Mo(CO)3] (16a/b), formed by transmetalation of Mo(CO)6, is oxidized by I2, yielding (pR)/(pS)-(1-menthyl-4,7-dimethylindenyl)Mo(CO)3I (17a/b). Depending on the reaction conditions, all compounds were formed as mixtures of diastereomers with respect to the planar chirality of the indenyl ring system. The diasteromeric excess varied between 9% and 71% de. Diastereomerically pure compounds were obtained after chromatography by dried alumina under nitrogen. The structures of 7a, 7b, 9a, 9b, and 14a were determined by single-crystal X-ray diffractometry.