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

Two novel extended chains based on rare {V(IV)(15)Si(6)O(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)(15)Si(6)O(48)} clusters are linked by a pair of V(V)O(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(15)Si(6)O(48)}-containing POMs. While in 2 the linkages are changed to [Co(pdn)(2)(H(2)O)](2+) (pdn = 1,3-propanediamine) cations instead of {V(V)O(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.