coupling is changed by the nature of the substituents on the cyclopentadienide rings; electron-withdrawing SiMe3 groups favor Yb(II), while electron-donating alkyl groups stabilize the Yb(III) species. The molecular structures of many of the compounds have been determined in the solid state, and the bond distances and angles are consistent with the interpretation of the magnetism. The ring substituents, and
将2,2′-联
吡啶基添加到抗磁性(Me 5 C 5)2 Yb(OEt 2)中,得到褐色加合物(Me 5 C 5)2 Yb(bipy)。溶液的1 H NMR和电子吸收光谱表明,联
吡啶配合物是顺磁性的,含有联
吡啶基阴离子,也可以在固态红外光谱和单晶X射线晶体学分析中检测到。然而,所测得磁矩,其从低于1个μ变化乙以5K至2.5μ乙在300 K,高于预期用于(ME 5 Ç 5)2的YbII(联
吡啶0)和小于预期(ME 5 Ç 5)2
镱III(联
吡啶- )。为
镱(III)之间的自旋耦合的电子交换模式,与电子组态4F 13,而在联
吡啶自由基阴离子单不成对电子被呈现,基于与所述
碘化物盐[(ME对比5 Ç 5)2
镱III( bipy 0)] + [I] -。比较(Me 5 C 5)2的磁化率Yb(phen)及其
碘盐与
菲咯啉作为
配体表现出相似的行为。顺磁性的程度以及因此的交换耦合因
环戊二烯环上取代基的性质而改变;吸电子的SiMe