Synthesis and structure of copper (II) complexes with L-OH (L-OH = 2,6 -bis -[N -(2 -pyridylethyl ) -formidoyl ] -4 -methyl -phenol)

Abstract The synthesis and molecular structures of three new copper (II) complexes with the ligand 2,6-bis-[ N -(2-pyridylethyl)-formidoyl]-4-methyl phenol (L–OH) are reported. The complexes were prepared by reaction of L–OH with CuX 2  ·  n H 2 O, affording [Cu 2 (L–O)(μ-OH)(μ-ClO 4 )](ClO 4 ) ( I ); X = CLO 4 - , with KOH in the reaction media; or [Cu 2 (L–O)(μ-Cl) 2 ][Cu 2 Cl 6 ] 0.5 ( II ); X = Cl, in neutral conditions. The presence of methyl 3,4-dihydroxy-benzoate (CAT-(OH) 2 ) during the synthesis of I leads to the complex [Cu 2 (L–O)(μ-OH)(CH 3 OH)][Cu(CAT-O 2 ) 2 ] 0.5 (ClO 4 ) ( III ). This compound exhibits an uncommon anion consisting of a bis-(catecholate) cuprate (II) moiety. The complete series of complexes show bridging phenoxo groups between the copper centers, together with hydroxo and perchlorate bridges found in I or two chlorides found in II . Compound I exhibit a rather low catalytic activity for the oxidation of 3,5-ditertbutyl catechol under aerobic conditions (12% quinone formation after 48 h at room temperature, in methanol solution 1 × 10 −3  M in catalyst and 1 × 10 −2  M in catechol), which could be ascribed to steric limitations of the catechol to coordinate the central Cu 2 O 2 core.