Copper Corroles Are Inherently Saddled

X-ray crystallographic analyses of two sterically unhindered copper meso-triarylcorroles, Cu[5,15-P2-10-(4-MeOP)C] and Cu[5,15-(4-CF3P)2-10-(4-MeOP)C] (P = phenyl and C = corrole), revealed substantially saddled corrole rings. These results are in marked contrast to those on highly sterically hindered cobalt(III) and iridium(III) corroles, which exhibit planar corrole macrocycles. The solution to this conundrum is that copper corroles are inherently saddled, as a result of a specific copper(d)−corrole(π) orbital interaction. This orbital interaction results in a noninnocent corrole ligand, and the overall electronic structure may thus be described as CuII−corrole•2−. While many specific metal(d)−macrocycle(π) orbital interactions are known for nonplanar metalloporphyrins, this work provides a rare example of such an orbital interaction providing the actual driving force for a significant nonplanar distortion. Our findings on copper corroles, along with those of others on cobalt and iridium corroles, thus constitute an intriguing and somewhat counterintuitive chapter in the structural chemistry of metallocorroles.

对两种立体无阻碍的铜中位三芳基腐胺Cu[5,15-P2-10-(4-MeOP)C]和Cu[5,15-(4-CF3P)2-10-(4-MeOP)C]（P代表苯基，C代表腐胺）进行X射线晶体学分析，揭示了显著的马鞍型腐胺环。这些结果与高度立体阻碍的钴(III)和铱(III)腐胺的研究结果形成鲜明对比，后者显示出平面的腐胺大环结构。解决这一谜题的关键在于铜腐胺本质上是马鞍型的，这是由于特定的铜(d)−腐胺(π)轨道相互作用所致。这种轨道相互作用产生了一个非惰性的腐胺配体，因此整个电子结构可以描述为CuII−腐胺•2−。尽管已知许多特定的金属(d)−大环(π)轨道相互作用与非平面金属卟啉有关，但这项工作提供了一个罕见的例子，表明这种轨道相互作用是实际驱动显著非平面扭曲的力。因此，我们对铜腐胺的研究，以及他人对钴和铱腐胺的研究，构成了金属腐胺结构化学中一个引人入胜且颇具反直觉的篇章。