Bimetals substituted germanotungstate complexes with open Wells-Dawson structure: Synthesis, structure, and electrochemical behavior of [{M(H2O)}(μ-H2O)2K{M(H2O)4}(Ge2W18O66)]11−(M = Co, Ni, Mn)

Reaction of the trivacant complex A-α-[GeW9O34]10− with transition metal cations (Co2+, Ni2+, Mn2+) yields four new germanotungstate heteropolyanions [Co4(H2O)2(GeW9O34)2]12− (1), [{Co(H2O)}1.33(μ-H2O)2K0.67{Co(H2O)4}(Ge2W18O66)]11− (2), [{Ni(H2O)}(μ-H2O)2K{Ni(H2O)4}(Ge2W18O66)]11− (3) and [{Mn(H2O)}(μ-H2O)2K{Mn(H2O)4}(Ge2W18O66)]11− (4). These complexes have been characterized by single-crystal X-ray analysis, IR, elemental analysis, UV–vis, TG, and electrochemistry. Polyanion 1 consists of two B-α-[GeW9O34]10− Keggin moieties related to a Weakley sandwich-type structure with C2h symmetry. Polyanions 2–4 consist of two A-α-[GeW9O34]10− associated through two W–O–W junctions. They derive from the Wells-Dawson structure by breaking four of the six W–O–W junctions. The pocket between the two-half-anions is filled by two transition metal cations. Compound 4 shows a three-dimensional structure constructed of two-dimensional polyoxometalates planes of [{Mn(H2O)}(μ-H2O)2K{Mn(H2O)4}(Ge2W18O66)]n11n- linked by K+ ions. Compounds 2–4 represent the first examples of two transition metals substituted germanotungstates with open Wells-Dawson structure type. The influence of the syntheses conditions of these four compounds has been studied. Furthermore, the stability and electrochemistry activity of compounds 1 and 2 are reported.