Chiral osmium complexes with sterically bulky schiff-base ligands. Crystal structures of Os(IV) derivatives and the reactivity and catalytic cyclopropanation of alkenes with EDA

Jing Zhang, Jiang Lin Liang, Xian Ru Sun, Hai Bing Zhou, Nian Yong Zhu, Zhong Yuan Zhou, Philip Wai Hong Chan, Chi Ming Che

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The syntheses and reactivities of sterically encumbered trans-dioxoosmium(VI) complexes containing Schiff-base ligands bis(3,5-di-tert-butylsalicylidene)-1,2-cydohexane-diamine (H2Bu- salch) and bis(3,5-dibromosalicylidene)-1,2-cyclohexane-diamine (H 2Br-salch) are described. Reactions of [OsVI(Bu-salch) O2] (1a) and [OsVI(Br-salch)O2] (1b) with PPh3, p-X-arylamines (X = NO2, CN), N2H 4·H2O, Ph2NNH2, SOCl 2, CF3CO2H, Br2, and I2 under reducing conditions gave [OsII(Br-salch)(OPPh3) 2] (2), [OsVI(Br-salch)(p-X-C6H 4NH)2] (3), [μ-O{OsIV(Bu-salch)(p-NO 2C6H4-NH)}2] (4), [Os II(Br-salch)(N2)(H2O)] (5), [Os IV(Bu-salch)(OH)(Cl)] (6), [OsIV(Bu-salch)(OH) 2] (7), [OsIV(Bu-salch)-Cl2] (8), [Os IV(Bu-salch)(CF3CO2)2] (9), [Os IV(Bu-salch)Br2] (10), and [OsIV(Bu-salch) I2] (11), respectively. X-ray crystal structure determinations of [OsIV(Br-salch)(p-NO2C6H4NH) 2] (3a), [OsIV(Br-salch)(p-CNC6H 4NH)2] (3b), 6, 8, 9, and 11 reveal the Os-N(amido) distances to be 1.965(4)-1.995(1) Å for the bis(amido) complexes, Os-Cl distances of 2.333(8)-2.3495(1) Å for 6 and 8, Os-O(CF3CO 2) distances of 2.025(6)-2.041(6) Å for 9, and Os-I distances of 2.6884(6)-2.6970(6) Å for 11. Upon UV irradiation, (1S,2S)-(1a) reacted with aryl-substituted alkenes to give the corresponding epoxides in moderate yields, albeit with no enantioselectivity. The (1R,2R)-6 catalyzed cyclopropanation of a series of substituted styrenes exhibited moderate to good enantioselectivity (up to 79% ee) and moderate trans selectivity.

Original languageEnglish
Pages (from-to)3942-3954
Number of pages13
JournalInorganic Chemistry
Issue number11
Publication statusPublished - 30 May 2005
Externally publishedYes

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