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.