| |
[摘要]：Mixed NHC-phosphine palladium(0) complexes [(NHC)Pd(PR3)] (NHC = N-heterocyclic carbene) are synthesized directly from com. available reagents, with the possibility to tune the nature of both the NHC and the phosphine. Reaction of [(NHC)Pd(allyl)Cl] (palladium source) and PR3, in the presence of a base afforded, in isopropanol, [(NHC)Pd-(PR3)] in good yields. It was found that the nature of solvent played a key role in efficient redn. of the PdII precursor to Pd0. Supported by exptl. evidence it was proposed that redn. step is driven by isopropoxide anion formed in situ from isopropanol and a base. Detection of acetone in the reaction mixt. confirms that the isopropoxide anion acts as the reducing agent. Moreover, different bases proved efficient for the reaction. The structures of the complexes were unambiguously confirmed by x-ray anal. Exposure of these complexes to air does not lead to decompn., but to the oxo-complex [(NHC)Pd(PR3)(O2)], which is stable both in the solid state and in soln. |
|
