Quercetin 2,3-Dioxygenase Mimicking Ring Cleavage of the Flavonolate Ligand Assisted by Copper. Synthesis and Characterization of Copper(I) Complexes [Cu(PPh3)2(fla)] (fla = Flavonolate) and [Cu(PPh3)2(O-bs)] (O-bs = O-Benzoylsalicylate)

Abstract

Cu(PPh3)2(fla) has been prepared by reacting copper(I) chloride with sodium flavonolate in tetrahydrofuran solution. Crystallographic characterization of the complex (orthorhombic, P212121, a = 9.588(1) A, b = 17.364(3) A, c = 24.378(3) A, V = 4058.6(10) A3, Z = 4, R = 0.049) has shown that the coordination geometry of the molecule is tetrahedral. Oxygenation of Cu(PPh3)2(fla) in a methylene chloride solution at ambient conditions gives the O-benzoylsalicylato copper complex Cu(PPh3)2(O-bs) and carbon monoxide. Labeling experiments with an 18O2−16O2 mixture (1:4) evidenced the incorporation of both 18O atoms of 18O2 into the O-bs ligand. IR and MS studies of labeled O-bs confirmed the incorporation of 18O2 while the released CO remained unlabeled. Crystallographic characterization of Cu(PPh3)2(O-bs) on crystals obtained as the acetone solvate (triclinic, P1, a = 13.154(1) A, b = 17.991(1) A, c = 20.495(1) A, α = 80.01(1)°, β = 88.02(1)°, γ = 71.83(1)°, V = 4537.5(5) A3, Z = 4, R = 0.0403) shows that the ...