Intramolecular Ligand Hydroxylation: Mechanistic Studies on the Reaction of a Copper(I) Schiff Base Complex with Dioxygen

The dinuclear copper(I) complex of 1,3-bis[N-(2-pyridylethyl)formimidoyl]benzene, [Cu(2)(H-BPB-H)(CH(3)CN)(2)](BF(4))(2), as well as the 5-nitro derivative, [Cu(2)(NO(2)-BPB-H)(CH(3)CN)(2)](BF(4))(2), react with dioxygen to form phenolate-bridged complexes as products. In a detailed kinetic study activation parameters of DeltaH() = 47 +/- 9 kJ/mol, DeltaS() = -53 +/- 11 J/(mol K), and DeltaV() = -9.5 +/- 0.5 cm(3)/mol for the reaction of [Cu(2)(H-BPB-H)(CH(3)CN)(2)](BF(4))(2) with dioxygen were obtained which account, together with further kinetic findings, for the occurrence of an intermediate peroxo complex that cannot be observed spectroscopically. The crystal structures of the products of the reaction were determined. Crystal data: complex [Cu(2)(H-BPB-O)-OH(H(2)O)](BF(4))(2), formula C(22)H(24)B(2)Cu(2)F(8)N(4)O(3), monoclinic space group P2(1)/c, Z = 4, a = 10.122(2) Å, b = 28.711(6) Å, c = 9.283(2) Å, alpha = 90 degrees, beta = 100.78(3) degrees, and gamma = 90 degrees; complex [Cu(2)(NO(2)-BPB-O)-OH(H(2)O)(3)](BF(4))(2), formula C(22)H(27)B(2)Cu(2)F(8)N(5)O(7), triclinic space group, P, Z = 2, a = 10.144(2) Å, b = 10.7612(2) Å, and c = 16.000(4) Å.