Copper-Mediated Hydroxylation of an Arene: Model System for the Action of Copper Monooxygenases. Structures of a Binuclear Cu(I) Complex and Its Oxygenated Product

Article abstract of DOI:10.1021/ja00319a036

A chemical system possessing features that mimic the structures and reactivity of the active sites of the copper oxygen carrier hemocyanin (Hc) and the monooxygenase tyrosinase (Tyr) is presented.When a dinuclear 3-coordinate Cu(I) complex, II, of a binucleating ligand, I, where the two tridentate nitrogen donor groups are separated by a m-xylyl bridge is reacted with dioxygen, the specific hydroxylation of the aromatic ring occurs in high yield (>90percent).This produces a binuclear pentacoordinate phenolato and hydroxo doubly bridged Cu(II) complex, IIIB.Manometric and mass spectrometric measurements utilizing isotopically labeled 18O2 show that the phenolate and hydroxy oxygen atoms in IIIB are derived from dioxygen, making this reaction an excellent biomimic for the action of the copper monooxygenases.Removal of the copper ions from IIIB gives a new phenol, IV, completing the sequence of the copper-mediated hydroxylation of an aromatic ring, I -> IV.Crystallographic studies have been completed on both II and III.II crystallizes in the triclinic space group P1/ with Z=2 and a=11.264(3) Angstroem, b=11.448(3) Angstroem, c=15.722(4) Angstroem, α=95.72(2) deg, β=102.05 deg, γ=94.77 deg.IIIB crystallizes in the monoclinic space group P2₁/, Z=4, with a=18.221(3) Angstroem, b=13.323(3) Angstroem, c=18.643(4) Angstroem, and β=102.39(2) deg.The structural features of these complexes are compared to those of other related compounds and to the active sites of the copper proteins.The biological relevance of the monooxygenase model system is also discussed.