Formation of vv lacunary polyoxovanadates and interconversion reactions of dodecavanadate species

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Oxidation, reactions of the reduced decavanadate [VIV2Vv8O26]4- (1) with halide guest anions were investigated for the synthesis of Vv host molecules. The reaction with Cl- afforded a new dodecavanadate, [HVV12O32(C1)]4-(3), which incorporated the guest chloride anion. The polyoxovanadate framework of 3 is different from, the bowl-shaped dodecavanadate [VV12O 32(CH3CN)]4- (2). The structure of 3 is regarded as a trilacunary counterpart of the pentadecavanadate [V V9VIV8O36C1] 4-. Employment: of an F-template yielded the layered polyoxovanadate [HVV11O29F2] 4- (4). The framework of 4 is a monolacunary structure of the fluoride-incorporated dodecavanadate [H6VV2VIv10O30F2] 6-, in which one of the VO groups at the belt position is removed. The three vana-dium atoms in the capping units are connected, by (μ3-F bridges. Reaction with Br provided [HVv12O32(Br)]4- (5) with minor formation of [H3VV10O28]3- Interconversion reactions between 2, 3, and 4 proceeded as follows: the reaction of 2 with Cl- prompted, an isomerization reaction of the bowl-type framework, affording 3; the reaction of 3 with F- gave 4; the reaction of 4 with CH3CN reproduced acetonitrile-incorporated 2. Complexes 3 and 4 were characterized by X-ray analysis. Polyoxovanadates 3 and 4, with the highest oxidation cores, exhibited distinct signals in the 51V NMR spectra, corresponding to lacunary polyoxovanadate geometries. © Wiley-VCH Verlag GmbH & Co. KGaA.
2009-11-02