Exploring the Metal-Centered Reactivity of Isomeric, N-Bridged Biscyclometalated Platinum(II) Complexes.

The field of platinum chemistry is ubiquitous in the research of anticancer drugs and new OLED materials. Within the vast library of existing compounds, the majority of work focuses on complexes in the +2 and +4 oxidation states, with comparatively few examples of Pt ^III complexes reported without bridging ligands. Pt ^III complexes with metal-metal bonding can be made by mild oxidation of Pt ^II complexes having bis(phenylpyridine) ligands. Here, we report the synthesis and characterization of two new Pt ^II complexes bearing tetradentate N-bridged bis(phenylpyridine) ligands with N^C*C^N and C^N*N^C coordinating atoms. Through chemical oxidation with PhICl ₂ and N-chlorosuccinimide, we obtained four new complexes containing Pt ^IV and Pt ^III centres. The dynamics of the Pt ^III  complexes were explored by variable-temperature NMR studies and showed surprisingly free rotation of the appended N-aryl group. This work uncovers the importance of the destabilizing nature of the bulky N-aryl group on intermetallic bonds, and sheds light on how the molecular rotation observed in the Pt ^III compounds could inspire new molecular rotors driven by intermetallic bonds.
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