Kinetic studies on the copper(II)-mediated oxygenolysis the flavonolate ligand. Crystal structures of [Cu(fla)_2] (fla = flavonolate) and [Cu(O-bs)_2(py)_3 ](O-bs = O-benzoylsalicylate)

摘要

The complex [Cu(fla)_2] has been prepared by treating copper(II) chloride with sodium flaonolate in tetrahydrofuran solution. Crystallographic characterisation of the ocmplex [Cu(fla)_2].2CHCl_3 has shown that the co-ordination geometry ground the copper(II) ion is square planar. Oxygenation of [Cu(fla)_2] in dimethylformamide solution at ambient conditions gives[Cu(O-bs)_2](O-bs = O-benzoylsalicylate) and carbon monoxide. Crystallographic characterisation of [Cu(O-bs)_2]on crystals obtained from pyridine as [Cu(O-bs)_2(py)_3].0.91 y revealed that the co-ordination geometry of the copper(II) ion is square pyramidal with trans O atoms of O-bs and N atoms of py ligands in basal and an N atom of py in apical position. The oxygenolysis of [Cu(fla)_2] in DMF was followed by electron spectroscopy and the rate constants were determined according to the rate law -d[Cu(fla)_2/dt=K[Cu(fla)_2[O_2]. The rate constant, activation enthalpy, entropy and free energy at 373K are as folows; k/mol dm~(-3) s~(-1) = (1.57±0.08)×10~(-2),#DELTA#H/kJ mol~(-1) = 53±6, #DELTA#S/J K~(-1) mol~(-1) = -138±11, #DELTA#G/kJ mol~(-1) = 105±2. The reaction fits a Hammett linear free energy relationship and a higher electron density on copper results in a faster oxygenation reaction.