title: A molecular placeholder strategy to access a family of transition-metal-functionalized vanadium oxide clusters.
abstract: Systematic access to metal-functionalized polyoxometalates has thus far been limited to lacunary tungsten oxide and molybdenum oxide clusters. The first controlled, stepwise bottom-up assembly route to metal-functionalized molecular vanadium oxides is now presented. A di-vacant vanadate cluster with two metal binding sites, (DMA)2[V12O32Cl](3-) (DMA = dimethylammonium) is formed spontaneously in solution and characterized by single-crystal X-ray diffraction, ESI mass spectrometry, (51)V NMR spectroscopy, and elemental analyses. In the cluster, the metal binding sites are selectively blocked by hydrogen-bonded DMA placeholder cations. Reaction of the cluster with transition metals TM (Fe(3+), Co(2+), Cu(2+), Zn(2+)) gives access to mono-functionalized vanadate clusters (DMA)[{TM(L)}V12O32Cl](n-) (L = ligand). Metal binding is accomplished by significant distortions of the vanadium oxide framework reminiscent of a pincer movement. Cluster stability under technologically relevant conditions in the solid-state and solution is demonstrated.
authors.affiliation: Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm (Germany), Fax: (+49) 731-50-23031 http://www.strebgroup.net; Previous address: Department of Chemistry and Pharmacy, Institute of Inorganic Chemistry II, Friedrich-Alexander-University Erlangen-Nuremberg, Egerlandstrasse 1, 91058 Erlangen (Germany).
authors.forename: Katharina
authors.initials: K
authors.lastname: Kastner
authors.forename: Johannes T
authors.initials: JT
authors.lastname: Margraf
authors.forename: Timothy
authors.initials: T
authors.lastname: Clark
authors.forename: Carsten
authors.initials: C
authors.lastname: Streb
keywords: functionalization; metal oxide clusters; polyoxometalates; polyoxovanadates; self-assembly