A study is reported on the relative stability of trivalent bis(ligand) complexes of the form [M(LR)2N′′] for trivalent group 3, lanthanide and actinide cations, using the sterically demanding N-heterocyclic carbene ligand LR = [OCMe2CH2CNCH2CH2NR}] (R = iPr LP, Mes LM, Dipp LD; N′′ = N(SiMe3)2). For the small YIII cation (r6-coord = 1.040 Å) and the smallest LR, R = iPr, mono, bis, and tris(LP) complexes can be made; [Y(LP)2N′′] and [Y(LP)3] have been characterised. For the larger ligands, LM and LD, only the mono(LR) complexes [Y(LM)N′′2] and [Y(LD)N′′2] can be made. For the larger CeIII (r6-coord = 1.15 Å), mono(LR) and bis(LR) complexes [Ce(LM)N′′2], [Ce(LD)N′′2], [Ce(LM)2N′′], and [Ce(LD)2N′′] can be made; structural characterisation of the latter two confirm the high degree of steric congestion. The new complex [U(LM)N′′2] has also been isolated. Despite the very similar radii of CeIII and UIII (r6-coord = 1.165 Å), the complexes [U(LR)2N′′] cannot be isolated; a surprising display of the difference between the 4f and 5f metal series. However, the six-coordinate, bis(ligand) UIV complexes can readily be isolated if smaller ancillary ligands are used; [U(LM)2I2] and [U(LD)2I2] have been fully, including structurally, characterised.
本文报告了一项关于三价双(
配体)[M(LR)2N′′]配合物相对稳定性的研究,该配合物为三价第 3 族
镧系元素和
锕系元素阳离子,使用的 N-杂环
碳配体 LR = [OCMe2CH2CNCH2CH2NR}] (R = iPr LP、Mes LM、Dipp LD;N′′ = N(SiMe3)2)。对于较小的 YIII 阳离子(r6-coord = 1.040 Å)和最小的 LR(R = iPr),可以制备出单、双和三(LP)配合物;[Y(LP)2N′′] 和 [Y(LP)3] 已经得到表征。对于较大的
配体 LM 和 LD,只能制作单(LR)配合物 [Y(LM)N′′2] 和 [Y(LD)N′′2]。对于较大的 CeIII(r6-coord = 1.对于较大的 CeIII(r6-coord = 1. 15 Å),可以制成单(LR)和双(LR)配合物 [Ce(LM)N′′2]、[Ce(LD)N′′2]、[Ce(LM)2N′′] 和 [Ce(LD)2N′′];后两者的结构特征证实了高度的立体拥塞。还分离出了新的复合物[U(LM)N′′2]。尽管 CeIII 和 UIII 的半径非常接近(r6-coord = 1.165 Å),[U(LR)2N′′] 复合物却无法分离出来;这令人惊讶地显示了 4f 和 5f
金属系列之间的差异。不过,如果使用较小的辅助
配体,六配位双(
配体)UIV 复合物很容易分离出来;[U(LM)2I2] 和 [U(LD)2I2] 已经得到了全面的表征,包括结构上的表征。