期刊
ACS CATALYSIS
卷 1, 期 12, 页码 1647-1653出版社
AMER CHEMICAL SOC
DOI: 10.1021/cs2004278
关键词
homogeneous gold catalysis; cycloaddition reaction; diaurate complex as catalyst; Au(I) complex as precatalyst
资金
- Spanish Ministry of Science and Innovation [CTQ 2009-11586]
- The Generalidad Valenciana
Bulky Au(I) biphenylphosphine complexes form with phenylacetlene isolable digold complexes under conditions of the room temperature intermolecular [2 + 2] cycloaddition of phenylacetylene and a-methylstyrene. Single-crystal X-ray diffraction (XRD) of two digold complexes show the presence of Au atoms connected to the C C triple bond of a phenylacetylene subunit through a a and a pi bond. The two Au atoms are fluxional and undergo exchange even at -80 degrees C. These digold complexes exhibit as catalysts almost complete selectivity toward the intermolecular cycloaddition and higher final yield to the corresponding cyclobutene than the corresponding mono Au(I) complex precursor. The difference in selectivity between the commercial mono Au(I) complex and the corresponding digold-phenylacetylene complex was found to be due to the generation of Bronsted acids of the counteranion [HSbF(6) or HN(CF(3)SO(2))(2) in the cases studied] that are formed by replacement of the C C H by a C C-Au bond. This Bronsted acid causes alpha-methylstyrene dimerization and degradation of the cyclobutene, two processes that do not occur when the reaction is promoted by the digold complex.
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