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-alpha-[GeW9O34](10-) with transition metal cations (Co2+, N i(2+), Mn2+) yields four new germanotung-state heteropolyanions [Co-4(H2O)(2)(GeW9O34)(2)](12-) (1), [{Co(H2O)}(1.33)(mu-H2O)(2)K-0.67{Co(H2O)(4)}(Ge2W18O66)](11-) (2), [{Ni(H2O)}(mu-H2O)(2)K{Ni(H2O)(4)}(Ge2W18O66)](11-) (3) and [{Mn(H2O)}(mu-H2O)(2)K{Mn(H2O)(4))(Ge2W18O66)](11-) (4). These complexes have been characterized by sinale-crystal X-ray analysis, IR, elemental analysis, UV-vis, TG, and electrochemistry. Polyanion 1 consists of two B-alpha-[GeW9O34](10-) Keggin moieties related to a Weakley sandwich-type structure with C-2h, symmetry. Polyanions 2-4 consist of two.4-alpha-[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)}(mu-H2O)(2)K{Mn(H2O)(4)}(Ge2W18O66)](n)(11n-) 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 I and 2 are reported. (C) 2006 Elsevier B.V. All rights reserved.