Self-assembly of [β-As(V)W8O31]9− subunit in hydrothermal system with moderate acidity: Synthesis, crystal structure and characterizations of dimeric arsenotungstate H2[{Cu(phen)}8(β-AsW8O31)2] · 2.5H2O

A novel dimeric arsenotungstate based on tetravacant subunit, H2[{Cu(phen)}8(β-AsW8O31)2] · 2.5H2O (phen = 1,10-phenanthroline) 1, has been prepared by hydrothermal methods. The title compound represents the first arsenotungstate example based on tetravacant Keggin polyanions. Furthermore, the comparison of β-Asw8O319- with few known tetravacant blocks exhibits the variety of XW8O31n- family in synthesis methods and existent forms.