Copper(II) complexes supported by bulky tridentate ligands L1H (N,N-bis(2-quinolylmethyl)-2-phenylethylamine) and L1Ph (N,N-bis(2-quinolylmethyl)-2,2-diphenylethylamine) have been prepared and their crystal structures as well as some physicochemical properties have been explored. Each complex exhibits a square pyramidal structure containing a coordinated solvent molecule at an equatorial position and a weakly coordinated counter anion (or water) at an axial position. The copper(II) complexes reacted readily with H2O2 at a low temperature to give mononuclear hydroperoxo copper(II) complexes. Kinetics and DFT studies have suggested that, in the initial stage of the reaction, deprotonated hydrogen peroxide attacks the cupric ion, presumably at the axial position, to give a hydroperoxo copper(II) complex retaining the coordinated solvent molecule (H R •S). H R •S then loses the solvent to give a tetragonal copper(II)-hydroperoxo complex (H R ), in which the -OOH group may occupy an equatorial position. The copper(II)-hydroperoxo complex H R exhibits a relatively high O-O bond stretching vibration at 900 cm-1 compared to other previously reported examples.
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Acknowledgments This work was financially supported in part by Grants-in-Aid for Scientific Research (No. 15350105 for SI) from the Ministry of Education, Culture, Sports, Science and Technology, Japan, by a Research Fellowship from the Japanese Society for the Promotion of Science for Young Scientists (for TO), and by the U.S. National Science Foundation (CHE-0203346 for CJC). The authors also thank Professor William B. Tolman of University of Minnesota for his helpful discussion and suggestions.
- Bis(quinolylmethyl)amine tridentate ligand
- Copper(II) complex
- DFT calculation
- Hydroperoxo copper(II) complex