Synthesis and structure of pillared molybdates and tungstates with framework layers

Abstract

Six new layered lanthanide molybdate and tungstate phases pillared by either naphthalenedisulfonate (NDS) or fumarate anions have been synthesized hydrothermally and structurally characterized. Five of these materials, [Nd(H(2)O)MoO(4)](2)[2,6-NDS] (1), [Nd(H(2)O)MoO(4)](2)[1,5-NDS] (2), [La(H(2)O)WO(4)](2)[1,5-NDS] (3), [La(H(2)O)WO(4)](2)[2,6-NDS] (4), and [Ce(H(2)O)MoO(4)](2)[fumarate] (6), have a closely related cationic inorganic layer structure which comprises a bilayer of polyhedra leading to the formation of a framework layer containing small, inaccessible pores. These layers are pillared by the organic anions which also bridge between the lanthanide cations within the layers. In the La/WO(4)/2,6-NDS system, a second polymorph, [La(2)(H(2)O)(2)W(2)O(8)][2,6-NDS] (5), is observed. In this compound, the tungstate anions have dimerized, forming W(2)O(8)(4-). This dimer is unique and comprises two square-based pyramidal tungsten centers which are opposed to each other.