The reaction between [XW(9)O(34)](9-) (X = As, P) and [RuC(6)H(6)Cl(2)](2) in aqueous buffer solution (pH 6.0) leads to the isolation of two pseudo-sandwich-type heteropolytungstates KNa(6)[(RuC(6)H(6))AsW(9)O(34)] x 17 H(2)O (As-1) and Na(7)[(RuC(6)H(6))PW(9)O(34)] x 14 H(2)O (P-2). Single-crystal X-ray diffraction analyses reveal that the two compounds have the following features: (1) in two polyanions [(RuC(6)H(6))XW(9)O(34)](7-) (X = As, 1; P, 2), the (RuC(6)H(6)) unit is linked via three Ru-O(W) bridges to the side of the trilacunary polyanion, while the lacunary site is still free; (2) the units 1 and 2 are connected exclusively by a central Na cation cluster to form the pseudo-sandwich-type heteropolytungstates; and (3) the pseudo-sandwich-type heteropolytungstates are further connected by Na or K cations to construct the 2D and 3D structures. Furthermore, the electrochemical behaviours of As-1 and P-2 in aqueous solution (1.0 M LiCl + HCl, pH 3.0) have been investigated. Two compounds exhibit the expected reduction processes of the W atoms in a negative potential range and the oxidation of the Ru center in a positive potential range. The results of the electrocatalytic experiments reveal that the compound P-2 has electrocatalytic activity towards the reduction of nitrate.