Bis((diphenyl)phosphinoxy)phenyl Platinum(II) Pincer Complexes: Substitution Reactions of Terminal Ligands and Electrocatalytic Proton Reduction Activity

ABSTRACT A synthetic methodology has been developed for novel platinum(II) pincer complexes bearing bis((diphenyl)phosphinoxy)phenyl ( Ph POCOP Ph ) ligand. Platinum(II) complexes of the type ( Ph POCOP Ph )Pt‐C≡CR [R = 4‐(2,1,3‐benzothiadiazolyl), phenyl] were synthesized via copper‐catalyzed reactions in the presence of amine bases. Treatment of the chloride complex ( Ph POCOP Ph )PtCl with a 10%–20% excess of copper halides or cyanide in the presence of amines afforded high yields of the new complexes ( Ph POCOP Ph )PtX [X = I, Br, CN]. The molecular structures of complexes with the iodine and σ‐(4‐benzothiadiazolylethynyl) ligands were determined by single‐crystal x‐ray diffraction. The IR and NMR spectroscopic data as well as the electrochemical properties of the new complexes were investigated, revealing correlations between their structures and reactivity. Electrochemical studies demonstrated that the halogen‐containing complexes effectively catalyze the hydrogen evolution reaction. Based on these results, a mechanistic pathway is proposed for the platinum(II)‐mediated electrochemical reduction of protons to hydrogen involving [( Ph POCOP Ph )Pt] intermediates.