Inverse palladocenes.

You, Qing; Jiang, Xue-Lian; Zhao, Yan; Gu, Wanmiao; Li, Jun; Wu, Zhikun · Nat Commun · 2026

basic_science · Level V

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Abstract

Metallocene research has influenced the development of organometallic chemistry, and the metal-nonmetal inverted half-sandwich structure (inverse metallocene) was very recently discovered. However, additional instances are required to propose the concept inverse metallocene and it remains uncertain whether metal five-membered ring structures analogous to the cyclopentadienyl anion structure exist. Herein we report the synthesis of a series of palladium analogs Pd<sub>8</sub>(PPh)<sub>2</sub>(PPh<sub>3</sub>)<sub>2</sub>(Ph<sub>2</sub>P=O)(S-Adm)<sub>5</sub> (Pd<sub>8</sub>-P), Pd<sub>6</sub>(PPh)(PPh<sub>3</sub>)(S-Adm)<sub>6</sub> (Pd<sub>6</sub>), Pd<sub>5</sub>(PPh)(S-Adm)<sub>4</sub>[(Ph<sub>2</sub>P)<sub>2</sub>O] (Pd<sub>5</sub>-O), and Pd<sub>5</sub>(PPh)(S-Adm)<sub>4</sub>[(Ph<sub>2</sub>P)<sub>2</sub>CH<sub>2</sub>] (Pd<sub>5</sub>-C), identify their fundamental metal building block named five-membered Pd aromatic ring, and reveal their conjugation‒photothermy correlation. In particular, we report an average NIR-II photothermal conversion efficiency per metal atom of 14.7% and the stability of the five-membered Pd aromatic ring, as illustrated by the fact that Pd<sub>5</sub>-C maintained photothermy performance for >10 heating-cooling cycles even after the ligands were removed. We further demonstrate the great potential of inverse palladocenes in areas such as laser shielding, high-temperature degradation, ignition, and temperature/light control. These results declare the research and application start of a type of materials named inverse palladocenes.