The (Z)-4-aryliden-2-(2-acetoxyphenyl)-5(4H)oxazolones 1a-1c react with H2SO4 to give the corresponding (Z)-4-aryliden-2-(2-hydroxyphenyl)-5(4H)oxazolones 2a-2c.The molecular structures of 1c and 2a have been determined by X-ray diffraction methods, and show planar skeletons. Oxazolones 2a-2c are potential C, N, O-tridentate ligands towards transition metals, and their molecular design obeys to the search of a rigid environment around the metal. The reaction of Pd(OAc)2 with oxazolones 2a-2c (1:1 M ratio) in CF3CO2H or NCMe as solvents results in the synthesis of diverse complexes (3–7). As a function of the reaction conditions, two different bonding modes have been characterized: N, O-chelate in the dinuclear complexes Pd(¿2-N, O-2b, c)(µ -O2CCF3)]2 (3b, c), as a result of the N-coordination and deprotonation of the hydroxy group; and C, N, O-tridentate in mononuclear complexes Pd(¿ 3-C, N, O-2a, b)(L)] (L = CF3CO2H 4a, b; dmso-d6 5a, b; NCMe 6b; pyridine 7b), obtained after N-bonding, OH deprotonation and C–H bond activation. All complexes have been fully characterized by HRMS and NMR methods, showing the high stability of the C, N, O-tridentate bonding mode.