Introducing organosilicone source into the synthetic system of polyoxovanadates: Two novel {V ₁₅Si ₆O ₄₈}-based extended chains

Two novel extended chains based on rare {V ^IV ₁₅Si ₆O ₄₈} have been prepared under hydrothermal conditions by introducing an organosilicone source into the synthetic system of the polyoxovanadates. Single-crystal X-ray diffraction analyses show that the neighboring {V ^IV ₁₅Si ₆O ₄₈} clusters are linked by a pair of V ^VO ₂ fragments via the coordination bonds of (Si-)O-V-O(-Si) to give rise to a zig-zag chain in compound 1, which is the first example of V(iv,v) mixed valence states successfully synthesized in {V ₁₅Si ₆O ₄₈}- containing POMs. While in 2 the linkages are changed to [Co(pdn) ₂(H ₂O)] ²⁺ (pdn = 1,3-propanediamine) cations instead of {V ^VO ₂} fragments, to generate another comparable 1-D infinite chain, which demonstrates the first organic-inorganic vanadosilicon hybrid linked by a second transition-metal complex. The possible hydrolysis mechanism of tetraethyl orthosilicate as the Si source is postulated to afford a feasible protocol to synthesize a new type of vanadosilicate cluster. The magnetic properties of the two compounds have also been investigated.