New Dinuclear Catalysts Rh2(N-O)2[(C6H4)P(C6H5)2]2 with Imidate Ligands: Synthesis and Isomerization from Head-t
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- 作者：Mario Barberis ; Francisco Estevan ; Pascual Lahuerta ; Julia Pé ; rez-Prieto ; and Mercedes Sanaú
- 刊名：Inorganic Chemistry
- 出版年：2001
- 出版时间：August 13, 2001
- 年：2001
- 卷：40
- 期：17
- 页码：4226 - 4229
- 全文大小：68K
- 年卷期：v.40,no.17(August 13, 2001)
- ISSN：1520-510X
文摘
Two new dirhodium(II) catalysts of general formula Rh2(N-O)2[(C6H4)P(C6H5)2]2 (N-O = C4H4NO2) are prepared,starting from Rh2(O2CCH3)2(PC)2L2 [PC = (C6H4)P(C6H5)2 (head-to-tail arrangement); L = HO2CCH3]. Thethermal reaction of Rh2(O2CCH3)2(PC)2·L2 with the neutral succinimide stereoselectively gives one compoundthat according to the X-ray structure determination has the formula Rh2(C4H4NO2)2[(C6H4)P(C6H5)2]2 (1). Itcorresponds to the polar isomer with two bridging imidate ligands in a head-to-head configuration. However,stepwise reaction of Rh2(O2CCH3)2(PC)2·L2 with (CH3)3SiCl and potassium succinimidate yields a mixture of 1and one of the two possible isomers (structure B) with a head-to-tail configuration of the imidate ligands, Rh2(C4H4NO2)2[(C6H4)P(C6H5)2]2 (2), also characterized by X-ray methods. In solution, compound 2 undergoes slowisomerization to 1; the rate of this process is enhanced by the presence of acetonitrile. Compounds 1 and 2 areobtained as pure enantiomers starting from (M)- and (P)-Rh2(O2CCH3)2(PC)2·L2 rather than from the racemicmixture. Their enantioselectivities in cyclopropanation of 1-diazo-5-penten-2-one are similar to those reportedfor the dirhodium amidate catalysts.