Ionothermal synthesis was applied to the formation of polyoxometalates (POMs) and two new compounds [EMIM](8)Na(9)[WFe(9)(micro(3)-O)(3)(micro(2)-OH)(6)O(4)H(2)O(SiW(9)O(34))(3)].7H(2)O (, [EMIM](8)Na(9)[].7H(2)O, EMIM = 1-ethyl-3-methylimidazolium) and [EMIM](4)[SiMo(12)O(40)].12H(2)O (), have been successfully produced in the ionic liquid (IL) [EMIM](4)Br. They were characterized by single-crystal X-ray diffraction, elemental analysis, UV-vis, IR and TG analysis. Furthermore, the magnetic properties of and the electrochemical properties of were studied. is a high-nuclear transition metal substituted polyoxometalate (TMSP) and the unprecedented polyoxoanion of is composed of three [alpha-SiW(9)O(34)](10-) Keggin moieties connected by a {WFe(9)} cluster core. is a heteropolyoxometalate with the polyoxoanion of alpha-Keggin type.