Not So Similar: Different Ways of Nb(V) and Ta(V) Catecholate Complexation

The reactions between catechol (H(2)cat) and niobium(V) or tantalum(V) precursors in basic aqueous solutions lead to the formation of catecholate complexes of different natures. The following complexes were isolated and characterized by single-crystal X-ray diffraction (SCXRD): (1) (NH(4))(3)[NbO(cat)(3)]∙4H(2)O; (2) K(2)[Nb(cat)(3)(Hcat)]·2H(2)cat·2H(2)O; (3) Cs(3)[NbO(cat)(3)]·H(2)O; (4) (NH(4))(4)[Ta(2)O(cat)(6)]·3H(2)O; (5) Cs(2)[Ta(cat)(3)(Hcat)]·H(2)cat; (6) Cs(4)[Ta(2)O(cat)(6)]·7H(2)O. The isolated crystalline products were characterized by elemental analysis, X-ray powder diffraction (XRPD), FTIR, and TGA. The structural features of these complexes, such as {Ta(2)O} unit geometry, Cs-π interactions, and crystal packing effects, are discussed.