Trigonal Pyramidal {AsO2(OH)} Bridging Tetranuclear Rare-Earth Encapsulated Polyoxotungstate Aggregates

The one-pot assembly reaction of Na2WO4·2H2O, RE(NO3)3·6H2O, and NaAsO2 in the participation of dimethylamine hydrochloride as an organic solubilizing agent in the acidic aqueous solution led to a class of trigonal pyramidal {AsO2(OH)} bridging rare-earth substituted arsenotungstate (AT) aggregates [H2N(CH3)2]8Na8{[W3RE2(H2O)8AsO8(OH)][B-α-AsW9O33]2}2·65H2O [RE = EuIII (1), GdIII (2), TbIII (3), DyIII (4), HoIII (5), YIII (6)], which were structurally characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, and thermogravimetric (TG) analyses. The common structural feature of 1–6 is that their polyoxoanions consist of a novel tetrameric unit [(W3RE2(H2O)8AsO8(OH))(B-α-AsW9O33)2]216– constituted by four trivacant Keggin [α-AsW9O33]9– fragments linked through an unseen elliptical [W6RE4(H2O)16As2O16(OH)2]20+ moiety. Their polyoxoanionic infrastructures can also be described as a fusion of two equivalent dimeric subunits [(W3RE2(H2O)8O7)(B-α-AsW9O33)2]8– bridged via two μ2-{AsO2(OH)...