Synthesis and characterization of orthopalladated complexes containing tridentate C,N,O-oxazolones

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,Otridentate 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(kappa 2-N,O-2b,c)(mu -O2CCF3)]2 (3b,c), as a result of the N-coordination and deprotonation of the hydroxy group; and C,N,Otridentate in mononuclear complexes [Pd(kappa 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.

Automated summary

The reaction between (Z)-4-aryliden-2-(2-acetoxyphenyl)-5(4H)oxazolones and H2SO4 results in the formation of (Z)4-aryliden-2-(2-hydroxyphenyl)-5(4H)oxazolones. These oxazolones can act as potential C,N,O-tridentate ligands towards transition metals, and the resulting complexes exhibit high stability.