AbstractComplexes [MCl2Cp*]2 (M=Ir, Rh), [RuCl2(p‐cymene)]2 and [Ir(C^N)2Cl]2 (HC^N=a, phenylpyridine ; b, phenylpyrazole,) react with imine ligands derived from ο‐aminophenol to yield complexes with an exocyclic C=N bond which has a cis or trans configuration. The trans isomer is favoured except for sterically crowded complexes Cp*M (M=Ir, Rh) when the imine has a mesityl substituent, for which the cis isomer is favoured. The complexes undergo photoisomerisation in visible light but revert back to the original isomer over time or when heated. The rate of the thermal reverse isomerisation depends on the imine substituent and the metal fragment. DFT calculations correctly reproduce the favoured isomer and suggest that the reverse isomerisation occurs by a rehybridisation at the N atom as found in organic imines. In addition, a triplet state, thermally accessible by a Minimum Energy Crossing Point (MECP) provides a low energy pathway for reverse isomerisation in the case of the half‐sandwich complexes.
摘要[MCl2Cp*]2(M=Ir、Rh)、[RuCl2(p-cymene)]2 和 [Ir(C^N)2Cl]2(HC^N=a,苯基
吡啶;b,苯基
吡唑)与来自 ο-aminophenol 的
亚胺配体反应,生成具有顺式或反式构型的外环 C=N 键的配合物。反式异构体更受青睐,但当
亚胺具有
间苯二酚取代基时,立体拥挤的配合物 Cp*M (M=Ir、Rh)则更受青睐,因为顺式异构体更受青睐。复合物在可见光下会发生光异构化,但随着时间的推移或加热后又会还原成原来的异构体。热反向异构化的速率取决于
亚胺取代基和
金属片段。DFT 计算正确地再现了受青睐的异构体,并表明反向异构化是通过有机
亚胺中 N 原子的再杂化发生的。此外,在半三明治复合物的情况下,通过最小能量交叉点 (MECP) 可热进入的三重态为反向异构化提供了低能途径。