REACTION OF MOLECULAR-OXYGEN WITH COPPER(I) - STRUCTURAL CHARACTERIZATION OF DIMERIC MU-CARBONATO AND TETRAMERIC MU-HYDROXO COMPLEXES RESULTING FROM THE AUTOXIDATION OF A COPPER(I) CARBONYL COMPLEX

Condensation of 1, 2-dicyanobenzene with 2-amino-4-methylpyridine yields the tridentate ligand 1, 3-bis(2-(4-methyl-pyridyl)imino)isoindoline, HL, 1. Reaction of HL with Cu(OAc)2 gives Cu(L)OAc, 2, while HL plus CuCl in the presence of triethylamine and carbon monoxide gives diamagnetic, presumably four-coordinate Cu(I)-containing Cu(L)CO, 3 (vco 2068 cm-1). This carbonyl complex, Cu(L)CO, reacts with dioxygen in dry benzene or toluene to give a variety of products, two of which were characterized by crystal structure determinations. A carbonate-bridged dimeric complex (CuL)2((μ-CO3), 4, in which the carbonate group presumably results from metal-promoted oxidation of CO via O2, crystallizes in the space group P1 with [FORMULA OMMITED] The structure was solved using 4578 reflections and gave R(F)=0.058. Each Cu(II) is approximately square planar, being coordinated to three nitrogen atoms of the tridentate ligand and to one oxygen atom of the bridging carbonate group. A hydroxyl-bridged tetrameric complex (CuL)3(CuLO)(μ-OH)3, 5, crystallizes with 2.5 benzene molecules and one water molecule per tetramer in the space group [FORMULA OMMITED] was obtained using 9334 reflections. The molecule contains two square-planar and two trigonal-bipyramidal Cu(II) atoms, each being coordinated to three nitrogen atoms of the tridentate ligand and linked in a linear array by three bridging hydroxyl groups. In addition a single oxygen atom, located on a pyridyl α carbon of the tridentate ligand, is distributed nonstatistically over the four tridentate ligands. This oxidation of the ligand presumably results from copper activation of dioxygen. © 1979, American Chemical Society. All rights reserved.