[(Mo12O30)-O-V(mu(2)-OH)(10)H-2{Ni-II(H2O)3}4], a highly symmetrical epsilon-Keggin unit capped with four Ni-II centers: Synthesis and magnetism

The novel title compound {(Ni4Mo12v)-Mo-II} demonstrates the concept of generating targeted spin topologies using reduced polyoxometalates: The four electrophilic nickel centers-forming a tetrahedron-are fixed by a nucleophilic highly reduced diamagnetic epsilon -Keggin cluster of T-d symmetry generated in solution. This cluster not only has a structural role but actually participates in the transmission of the exchange interaction.