Tuning of Electronic Properties and Reactivity in Four-Coordinate Cobalt(III) Complexes by the Tetraazamacrocyclic Tropocoronand Ligand.

Abstract

The syntheses of cationic, four-coordinate cobalt(III) complexes, [Co(TC-3,3)]+ and [Co(TC-4,4)]+, afforded by the tetraazamacrocyclic tropocoronand ligand [(TC-n,m)]2-, are described. The [Co(TC-4,4)]+ cation displays a unique geometry for tetracoordinate Co(III) between square-planar and tetrahedral. The reduction potentials and Lewis acidity of the [Co(TC-n,m)] tropocoronands, together with an extended Huckel MO analysis of the frontier orbitals, demonstrate electronic tuning through geometric variations imposed by the ligands.