The Oxalato-Titanium-Containing Tungstophosphate(V) Dimers, [Ti8(C2O4)8P2W18O76(H2O)4]18− and [Ti6(C2O4)4P4W32O124]20−

Abstract

The oxalato-titanium(IV)-containing, dimeric 18-tungsto-2-phosphate [Ti8(C2O4)8P2W18O76(H2O)4]18− (1) and the 32-tungsto-4-phosphate [Ti6(C2O4)4P4W32O124]20− (2) are formed upon reaction of the oxalato-titanium complex [TiO(C2O4)2]2− with the trilacunary Keggin precursor [A-α-PW9O34]9− and the hexalacunary Wells–Dawson precursor [H2P2W12O48]12−, respectively. Polyanion 1 consists of two {PW9} units encapsulating eight titanium centers and connected to each other via two Ti–O–Ti bridges, and crystallizes as a mixed potassium-sodium-lithium salt in the triclinic space group . Polyanion 2 comprises two {P2W16} units containing each two titanium atoms, and the two half-units are connected via two titanium atoms decorated by two oxalate groups each, and crystallizes as a mixed potassium-lithium salt in the rhombohedral space group . Polyanions 1 and 2 were characterized in the solid state by single-crystal XRD, FT-IR, and TGA, whereas polyanion 2 was also investigated by 31P and 183W NMR.