Dialkylamino cyclopentadienyl ruthenium(<scp>ii</scp>) complex-catalyzed α-alkylation of arylacetonitriles with primary alcohols
作者:Hung Wai Cheung、Juan Li、Wenxu Zheng、Zhongyuan Zhou、Yu Hin Chiu、Zhenyang Lin、Chak Po Lau
DOI:10.1039/b917805h
日期:——
Aminocyclopentadienyl ruthenium complexes, [(η5-C5H4NMe2)Ru(PPh3)2(CH3CN)]+BF4â and [(η5-C5H4NEt2)Ru(PPh3)2(CH3CN)]+BF4â, are moderately active catalysts for α-alkylation of arylacetonitriles with primary alcohols; on the other hand, the analogous unsubstituted cyclopentadienyl ruthenium complex [(η5-C5H5)Ru(PPh3)2(CH3CN)]+BF4â shows very low catalytic activity. On the basis of experimental results and theoretical calculations, rationalization for the much higher catalytic activity of the aminocyclopentadienyl complexes over that of the unsubstituted Cp complex is provided. In the catalytic systems with the former, it is possible to regenerate the active solvento complexes via protonation of the metal hydride intermediates and subsequent ligand substitution; this process is, however, very nonfacile in the catalytic system with the latter.
氨基环戊二烯基钌配合物 [(η⁵-C₅H₄NMe₂)Ru(PPh₃)₂(CH₃CN)]⁺BF₄⁻ 和 [(η⁵-C₅H₄NEt₂)Ru(PPh₃)₂(CH₃CN)]⁺BF₄⁻ 是对芳基乙腈与初级醇的α-烷基化反应具有适度活性的催化剂;另一方面,类似的未取代环戊二烯基钌配合物 [(η⁵-C₅H₅)Ru(PPh₃)₂(CH₃CN)]⁺BF₄⁻ 显示出非常低的催化活性。根据实验结果和理论计算,对氨基环戊二烯基配合物相较于未取代Cp配合物的催化活性显著更高的原因进行了合理解释。在采用前者的催化体系中,可以通过金属氢化物中间体的质子化和随后的配体置换来再生活性溶剂配合物;然而,在后者的催化体系中,这一过程则非常不易。