Synthesis, characterization and crystal structure of a novel Os(II)-supported tungstoarsenate [HAsW7O28Os(dmso)3]6−

Reaction of tri-lacunary Keggin tungstoarsenate with osmium complex Os(dmso)4Cl2 under mild condition led to the formation of a novel Os (II)-supported tungstoarsenate Na5(NH4)[HAsW7O28Os(dmso)3]·15H2O (1a). Single-crystal X-ray diffraction analysis shows that compound 1a crystallizes in the monoclinic space group P21/c (no. 14) with a=14.9166(12) Å, b=23.6935(19) Å, c=16.5349(14) Å, β=92.7950(10)°, V=5836.9(8) Å3, Z=4 with R1=0.0453. The crystal structure reveals two features: (1) the polyanion [HAsW7O28Os(dmso)3]6− (1) consists of a Os(dmso)3 unit linked to a tungstoarsenate fragment {HAsW7O28} via two Os–O–W bonds and one Os–O–As bond resulting in an assembly with Cs symmetry, which represents a novel mode of Os-coordination to a polyoxoanion framework; (2) 3D architecture assembled by the polyanion 1 and sodium linkers. In addition, the compound 1a was well characterized by the multinuclear NMR (13C, 1H), IR spectroscopy, UV–vis spectroscopy, elemental analysis, and cyclic voltammetry (CV).