The “Enders Triazole”: A well known molecule, but still a new ligand!!

Abstract 1,3,4-Triphenyl-1,2,4-triazolium salts have previously been used and described in the literature as precursors for carbenes, which have been reported as organocatalysts and as neutral monodentating N-heterocyclic carbene (NHC) ligands. We now report the synthesis of 1,3,4-tri-phenyl-4,5-dihydro-1 H -1,2,4-triazole-5-ylidene-platinum(II)-acetylacetonate where the triazole binds to the metal in a new coordination mode (C^C*) as an anionic bidentate ligand, where the NHC carbene interacts with the platinum center and one of the phenyl rings is cyclometalated. The complex shows phosphorescent emission in the blue region of the visible spectrum at 441 and 465 nm with a quantum yield of 42%. DFT calculations (BP86/6-31G* as well as B3LYP/6-31G*) were found to be well suited to determine the structure of the complex.