216
Catalysis of “outer-phase” oxygen atom exchange reactions by encapsulated “inner-phase” water in {V15Sb6}-type polyoxovanadates
M. Wendt, U. Warzok, C. Näther, J. van Leusen, P. Kögerler, C.A. Schalley, W. Bensch – 2016
Four new heteroatom-modified polyoxovanadate (POV) clusters {M(en)3}3[V15Sb6O42(H2O)x] (M = FeII, CoII, NiII) have been prepared under solvothermal conditions. Depending on the reaction conditions, two pseudopolymorphs of the nickel compound are obtained. In contrast to other POVs, these compounds are well soluble in water and thus permit post-functionalisation in solution. The clusters’ magnetic characteristics reflect the individual contributions of the frustrated {V15} spin polytope and the {M(en)3}2+ complexes, with very weak coupling between these groups. Electrospray ionisation mass spectrometry provides evidence (i) for a water molecule encapsulated inside the cavities of a fraction of the clusters, (ii) for a post-functionalisation in water, namely a slow exchange of VO against Sb2O, (iii) for the inner-phase reactivity of the encapsulated water that is capable of opening an oxo-bridge, and (iv) for a significant acceleration of the 16O/18O exchange reactions of oxygen atoms in the cluster periphery with surrounding H218O, when encapsulated water is present. To the best of our knowledge, this is the first example in polyoxovanadate chemistry for the transduction of inner-phase reactivity of an encapsulated guest molecule into changes in the outer-phase reactivity of the cluster.
Catalysis of “outer-phase” oxygen atom exchange reactions by encapsulated “inner-phase” water in {V15Sb6}-type polyoxovanadates