Lanthanide–Nitrogen Triple Bonds
Zhanxin Jiang, Ziqi Hu, Jingyao Ye, Yang-Rong Yao, Xinyi Han, Weiren Cheng, Muqing Chen, Yuan-Zhi Tan, Wenjing Hong, Zheng Jiang, Bingbao Mei, Alexey A. Popov, Shangfeng Yang, Su-Yuan XieAbstract
Lanthanide–ligand multiple bonds are difficult to stabilize due to the dominating ionic bonding nature of lanthanide metals, and solid-state synthesis of a lanthanide complex bearing a lanthanide–nitrogen triple bond has long been expected but never been reported. Here, we stabilize the lanthanide–nitrogen triple bond in solid state for the first time, in the form of a diatomic monocation CeN+ captured in a nitrogen-substituted carbon cage C81N–, namely, CeN@C81N with two cage isomers. Single-crystal X-ray diffraction results reveal the existence of Ce≡N triple bonds with bond lengths of 1.76 Å, which is much shorter than the shortest Ce═N double bond ever recorded (2.04 Å). Quantum-chemical studies reveal the formal Ce4+ valence state with enhanced 4f electron contribution to the Ce≡N triple bond, resulting in an electronic structure of [Ce4+≡N3–]+@[C81N]− featuring an unprecedented intramolecular single-electron transfer.