Two series of heteroleptic platinum(II) carbene compexes of the type [Pt(C∧C*)(O∧O)] (O∧O = acetylacetonate) with C∧C* cyclometalated 4-phenyl-1,2,4-triazol-5-ylidene as well as 1-phenyl-1,2,4-triazol-5-ylidene ligands were prepared. The effect of various substituents in the 4-position of the phenyl ring (4-phenyltriazole: H, Cl, OCH3, NO2; 1-phenyltriazole: H, Cl, OCH3, CH3) was studied. The ligand precursors were obtained by quaternization of the corresponding aryl-1,2,4-triazoles with iodomethane. The complexes were synthesized by a reaction sequence starting from the triazolium precursors via the silver(I) carbenes, transmetalation with dichloro(1,5-cyclooctadiene)platinum(II), cyclometalation reaction, and finally addition of acetylacetonate. All complexes have been characterized by standard techniques such as 1H NMR, 13C NMR, and elemental analysis. Additionally, solid-state structures of seven complexes could be obtained by single-crystal X-ray diffraction. According to absorption and emission spec...