Linear Chain Formation by an Oxovanadium(V) Complex of p-Methylhexahomotrioxacalix[3]arene

The oxovanadium(V) complex 4 can be readily synthesized by the reaction of the lithium salt of p-methylhexahomotrioxacalix[3]arene trianion 3 with VOCl(3). Infrared spectra indicate a terminal V=O for complex 4 in solution and V=O.V dative interactions in the solid state consistent with the formation of a -oxo-bridged linear chain polymer 1 (M = V, Y = O, X(3) = trianion of macrocycle 2a). Vanadium-51 NMR spectra indicate increased shielding for the linear chain polymer in the solid state compared to complex 4 in solution. Complex 4 and its linear chain polymer are proposed to have the oxovanadium group contained within the cup of the macrocycle ligand as shown in structures 5 and 7, respectively, where the cone represents macrocycle 2a.