New assembly of transition metal complexes based on [GeW9O34]10− building blocks: Syntheses, crystal structures and magnetic properties

Two new polyoxotungstates Na3H(C3H5N2)4[{Cu(C3N2H4)2}2Cu4(H2O)2(GeW9 O34)2]·27H2O (1) and Na10H8[Mn6Ge3W24O94(H2O)2]·37H2O (2) have been synthesized in aqueous solution. The polyoxoanion frameworks of the two compounds are built on the lacunary Keggin-type polyanion [GeW9O34]10−. The structure of compound 1 is a Weakley-type species capped by two [Cu(C3N2H4)2]2+ units through four bridging oxygen atoms on two opposite W4O4 faces. Compound 2 is a banana-shaped polyoxometalate consisting of two tri-Mn substituted [Mn3GeW9O34]4− Keggin units and a hexavacant bridging cluster [GeW6O26]12−. The magnetic investigations demonstrate the presence of both antiferromagnetic and ferromagnetic exchange interactions for 1 and weak antiferromagnetic interactions for 2.