Inverse palladocenes

Area of Science:

• Organometallic Chemistry
• Materials Science
• Nanotechnology

Background:

• Metallocene chemistry has advanced organometallic research.
• The concept of inverse metallocenes (metal-nonmetal inverted half-sandwich structure) is recently discovered.
• Existence of metal five-membered ring structures analogous to cyclopentadienyl anion is uncertain.

Purpose of the Study:

• To synthesize and characterize novel palladium-based inverse metallocene analogs.
• To identify the fundamental metal building block and its properties.
• To investigate the photothermal conversion efficiency and stability of these new materials.

Main Methods:

• Synthesis of palladium complexes: Pd₈(PPh)₂(PPh₃)₂(Ph₂P=O)(S-Adm)₅ (Pd₈-P), Pd₆(PPh)(PPh₃)(S-Adm)₆ (Pd₆), Pd₅(PPh)(S-Adm)₄[(Ph₂P)₂O] (Pd₅-O), and Pd₅(PPh)(S-Adm)₄[(Ph₂P)₂CH₂] (Pd₅-C).
• Structural identification of the five-membered palladium aromatic ring as the core building block.
• Evaluation of photothermal conversion efficiency in the near-infrared-II (NIR-II) region and assessment of material stability through heating-cooling cycles.

Main Results:

• Successful synthesis of four novel palladium complexes exhibiting inverse palladocene structures.
• Identification of a stable five-membered palladium aromatic ring as the fundamental unit.
• Achieved an average NIR-II photothermal conversion efficiency of 14.7% per metal atom.
• Demonstrated exceptional stability, with Pd₅-C maintaining photothermal performance over 10 cycles even after ligand removal.

Conclusions:

• The study establishes the existence and synthesis of inverse palladocenes with a unique five-membered palladium aromatic ring.
• These materials possess significant NIR-II photothermal conversion capabilities and high stability.
• Inverse palladocenes show great potential for applications including laser shielding, high-temperature degradation, ignition, and precise temperature/light control.