INOR 39 |
| The multigram synthesis of macrocyclic tetraimidazolium salts and their conversion to the first examples of homoleptic crown N-heterocyclic carbene complexes with later transition elements is described. The ligands show remarkable flexibility of coordination mode, enabling the formation of complexes in which one (Co(II), Ni(II), Pd(II)) or two (Cu(I), Ag(I) see figure below) metal ions are encapsulated in the macrocycle cavity. To date, linear, square planar and tetrahedral (but not octahedral) coordination geometries have been observed. The cobalt(II) complex undergoes reversible one electron oxidation and reduction. The oxidised species is apparently a rare example of a tetrahedral cobalt(III) complex, while the reduced cobalt(I) complex is utilised as a one electron reductant in various organic reactions. In the mononuclear complexes the metal ion is well shielded by the ligand framework, while the dinuclear complexes have a completely different ligand conformation, which enables association in the solid state to form “molecular wires”.
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Synthetic Coordination Chemistry
8:30 AM-12:30 PM, Sunday, August 19, 2007 BCEC -- 213, Oral
Division of Inorganic Chemistry |
