title: Stereoselective ligand-exchange reaction of planar-chiral cyclopentadienyl-ruthenium complexes: thermodynamic control of configuration at a stereogenic metal center.
abstract: The reaction of planar-chiral cyclopentadienyl-ruthenium complexes with Bu4NI resulted in the formation of iodo complexes with high diastereoselectivity (up to >99%de). The stereochemistry of the ruthenium center in the starting material did not influence the diastereoselectivity of the products. Epimerization of a diastereomerically pure sample gave a mixture of two diastereomers in the same ratio as with the ligand-exchange reaction, suggesting that the selectivity is determined by the difference in thermodynamic stability between the diastereomeric pair of iodo complexes. The ratio of the products depends on the nature of the substituent on the cyclopentadienyl ring and P ligands on the ruthenium atom. A combination of small substituents on the cyclopentadienyl group and small P ligands with strong electron-donating ability favored the formation of 2-I. The bulkiness of the substituents on the cyclopentadienyl group or of the P ligands, and low electron-donating ability of the P ligands increased the ratio of 2-II complexes to 2-I isomer.
authors.affiliation: The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Matsushima
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Onitsuka
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Takahashi
mesh_terms: D018360:Crystallography, X-Ray; D003517:Cyclopentanes / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry*; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D003517:Cyclopentanes; D008024:Ligands; D009942:Organometallic Compounds; D012428:Ruthenium