Cobalt(II)-mediated Oxygenation of a Macrocyclic Ligand. X-ray Structures of the Cobalt(II) and Cobalt(III) Products

Diaquo(5,7-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,7-diene)cobalt(II) hexafluorophosphate, [Co([14]4,7-dieneN4)(OH2)2](PF 6)2, reacts with O2 to form a new macrocyclic ligand ([14]4,7-dieneN4-one) with a ketone oxygen on the central carbon of the 2,4-pentanediiminato moiety. The cobalt(II) center appears to be necessary for this reaction yet is not oxidized in the process. The crystal and molecular structures of [Co([14]4,7-dieneN4-one)(OH2)2](ClO 4)2 and [Co([14]4,7-dieneN4-one)Cl2]ClO4 have been determined from three-dimensional x-ray data collected on an automatic diffractometer using Mo Kα radiation. The crystals of [Co([14]4,7-dieneN4-one)(OH2)2](ClO 4)2 belong to the space group P21/c with a = 10.371 (2) Å, b = 15.055 (3) Å, c = 14.467 (3) Å, β = 106.39 (2)°, and Z = 4. The crystals of [Co([14]4,7-dieneN4-one)Cl2]ClO4 belong to the space group Pbca with a = 12.030 (2) Å, b = 12.995 (2) Å, c = 23.523 (4) Å, and Z = 8. Full-matrix least-squares refinement yielded conventional discrepancy factors of 0.062 for 1835 observed counter data and 0.038 for 1894 observed counter data, respectively. The ketone oxygen in both complexes is bent up from the plane of the two imine bonds.