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(−)-2-Menthylindenyl and (−)-2-Menthyl-4,7-dimethylindenyl Complexes of Rhodium, Iridium, Cobalt, and Molybdenum

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journal contribution
posted on 13.11.2001, 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 (−)-2-menthylindene and (−)-2-menthyl-4,7-dimethylindene are described. Metathetic reaction of the chiral lithium salts of these indenyl systems (1, 2) with the appropriate starting materials of Rh and Ir yielded the complexes (−)-(2-menthylindenyl)Rh(COD) (3), (−)-(2-menthyl-4,7-dimethylindenyl)Rh(COD) (4), (−)-(2-menthylindenyl)Rh(C2H4)2 (5), (−)-(2-menthyl-4,7-dimethylindenyl)Rh(C2H4)2 (6), (−)-(2-menthylindenyl)Ir(COD) (7), (−)-(2-menthylindenyl)Ir(C2H4)2 (8), (−)-(2-menthyl-4,7-dimethylindenyl)Ir(C2H4)2 (9), and (−)-(2-menthyl-4,7-dimethylindenyl)Ir(COE)2 (10). Co2(CO)8 and CoCl2(dppe) react with (−)-2-menthylindenyllithium (1) yielding (−)-(2-menthylindenyl)Co(CO)2 (11) and (+)-(2-menthylindenyl)Co(dppe) (12). (−)-Li[(2-menthylindenyl)Mo(CO)3](THF)2 (13), formed by transmetalation of Mo(CO)6, is oxidized by I2, yielding (−)-(2-menthylindenyl)Mo(CO)3I (14), or by allylic chloride, yielding (allyl)(2-menthylindenyl)Mo(CO)2 (15). All compounds were formed stereomerically pure and were obtained after chromatography by dried alumina under nitrogen. The structures of 3, 4, 6, 7, and 14 were determined by single-crystal X-ray diffractometry. Variable temperature 1H NMR spectra of 5, 6, 8, and 9 were recorded to determine the energy barriers for rotation of ethylene along the metal−indenyl and metal−ethylene axes.

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