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Title: Rhodium Complexes of PCNHCP Ligand: Oxidative Addition of Dichloromethane and Catalytic Hydrosilylation of Alkynes Affording (E)-Allenylsilanes
Authors: Zeng, Jing-Yao;Hsieh, Meng-Hua;Lee, Hon Man
Contributors: 化學系
Date: 2005-12
Issue Date: 2014-08-14T04:29:04Z
Publisher: Elsevier
Abstract: New rhodium complexes of PCNHCP have been synthesized by using the silver transfer reagent, [Ag3(PCNHCP)2Cl]Cl2 (2). In the reaction between 2 and [Rh(COD)Cl]2 in dichloromethane, the presumably formed nucleophilic RhI(PCNHCP)Cl intermediate (A), undergoes a C–Cl bond activation of CH2Cl2 giving cis,mer-RhIII(PCNHCP)(CH2Cl)Cl2 (3) as the final product. Attempts to isolate A affords the oxidative degradation product of mer-RhIII(PCNHCP)Cl3 complex (4). In contrast, the rhodium(I) center in Rh(PCNHCP)(CO)Cl (5) is stabilized by the π-back bonding of CO ligand; a robust complex is, therefore, obtained. The solid-state structures of 2 and 3 were determined by X-ray diffraction. Complexes 3–5 are catalyst precursors for efficient, chemoselective hydrosilylation of alkynes. For the reaction between phenylacetylene and dimethylphenylsilane, a rapid hydrosilylation occurs, producing isomers of alkenylsilanes; then a slow isomerization pathway converts (Z)-alkenylsilane to its (E)-isomer. For 3, under catalytic condition, a facile reductive elimination of dichloromethane giving A is anticipated. The similarity in reactivity and selectivity between 3, 4 and 5 suggests the involvement of A as the active species in a common catalytic cycle.
Relation: Journal of Organometallic Chemistry, 690(24-25): 5662-5671
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