OXOVANADIUM(IV) AND OXOVANADIUM(V) COMPLEXES WITH AMINOALCOHOL LIGANDS - SYNTHESIS, STRUCTURE, ELECTROCHEMICAL, AND MAGNETIC-PROPERTIES

The aminoalcohol ligands diethanolamine (H(2)dea) and triethanolamine (H(3)tea) react with [VO(acac)(2)] to yield the tetranuclear oxovanadi um(IV) complexes [{VO(dea)}(2){VO(acac)}(2)(mu(2)-OMe)(2)] (1) and [{V O(Htea)}(2){VO(acac)}(2)(mu(2)-OMe)(2)] (2). In the case of the potent ially bridging aminoalcohol ligands N,N,N', N'-tetrakis (2-hydroxyethy l)ethylenediamine (H(4)edte) and N,N,N',N'-tetrakis(2-hydroxypropyl)e thylenediamine (H(4)edtp) the corresponding oxovanadium(N) complexes c ould not be isolated. Instead after air oxidation the ligand supported binuclear oxovanadium(V) complexes [{VO(acac)]}(2)(edte)] (3) and [{V O(acac)}(2)(edtp)] (4) are obtained. The reaction of the ligand H,edtp with ammonium meta-vanadate in methanol solution leads to the methoxy bridged binuclear oxovanadium(V) complex [(VO)(2)(edtp)(mu(2)-OMe)(2) ] (5). The tetranuclear oxovanadium(IV) complexes can be isolated as c rystalline compounds 1.2 MeOH and 2.2 MeOH and have been characterized by IR, UV/Vis, and ESR spectroscopy as well as cyclic voltammetry and magnetic susceptibility measurements. Single-crystal diffraction stud ies reveal that the complexes 1 and 2 contain a tetranuclear {(VO)(4)( mu(3)-OR)(2)(mu(2)-OR)(4)}(2+) core composed of three different types of edge-shared binuclear units, whereas the oxovanadium(V) complexes 3 , 4, and 5 posses binuclear structures, that are either Ligand support ed as in the case of 3 and 4 or contain a mu(2)-methoxy bridged {(VO)( 2)(mu(2)-OR)(2)}(4+) core as in the case of 5. ESR and magnetic data i ndicate a singlet ground state for 1.2 MeOH and 2.2 MeOH, although com peting ferromagnetic exchange interactions are operative within the te tranuclear core structure. In the solid state compounds 1.2 MeOH and 2 .2 MeOH hydrogen bridged supramolecular structures are found. The hydr ogen bonding scheme of both compounds leads to the formation of a simi lar chain arrangement of the tetranuclear complexes 1 and 2.