Fluorine-19 nuclear magnetic resonance studies of mixed bis(η6-arene)chromium(0) complexes
作者:H. Ssekaalo、J.J. Lagowski、C.M. Seymour
DOI:10.1016/s0020-1693(00)82999-0
日期:1991.5
conducted on mixed bis(η6-arene)chromium(0) complexes containing (CH3)m (m=1, 2 or 3) substituents in one of the partner arenes and CF3 or Fn, (n=1 or 2) substituents in the other arene. There is deshielding of the 19F in the (C6H6−m(CH3)m)-(C6H5CF3)Cr complex (I) relative to that in (C6H5CF3)2Cr(II). However, increased shielding of 19F is observed in the (C6H6−m(CH3)m)-(C6H6−nFn)Cr complex (III) relative
摘要已对其中一个伴有芳烃和CF3或Fn(n = 1)中含有(CH3)m(m = 1、2或3)个取代基的双(η6-芳烃)铬(0)混合配合物进行了19F NMR研究。或2)另一个芳烃中的取代基。相对于(C6H5CF3)2Cr(II),(C6H6-m(CH3)m)-(C6H5CF3)Cr络合物(I)中的19F脱屏蔽。但是,相对于(C6H6-nFn)2Cr(IV),在(C6H6-m(CH3)m)-(C6H6-nFn)Cr络合物(III)中观察到19F的屏蔽作用增强。看来CF3中的氟具有独特的行为,这受一系列复杂的电子电荷运动的影响,这主要是由于向(C6H6-m(CH3)m)芳烃的返电荷增加以及一个芳烃的取代基效应的传递所致。铬中心转移到伴侣的芳烃上;另一方面,III中19F共振的高场位移 之所以在某种程度上合理化,是因为对含Fn的芳烃有更大的背向捐赠,以及金属中心所传递的(CH3)m的电子释放效应。(1