Synthesis and Structural Characterization of Non-Homoleptic Carbamato Complexes of V(V) and W(VI) and Their Facile Implantation onto Silica Surfaces

The vanadium(V) amido-carbamato derivatives VO(NR2)(O2CNR2)2 (R = Me, 1; Et, 2) were obtained by reaction of VOCl3 with preformed carbamato species (ammonium or sodium carbamates). The synthesis of an ionic ammonium chlorido-amide of W(VI), 3, was performed using WOCl4 and diethylamine as precursors. Moreover, reactivity of 3 with CO2 was investigated. Mixed W(VI) chlorido-carbamato compounds, 4-5, were obtained by reaction of WOCl4 with stoichiometric amounts of sodium diethylcarbamate. All the products were characterized by analytical and spectroscopic methods (IR, multinuclear NMR), and by X-ray diffraction in the cases of 3 and 4. DFT calculations were useful to elucidate the structures of the compounds and to give insight into the various reaction pathways. The combination of 2 or 5 with amorphous silica gave solid materials which were characterized by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Energy Dispersive X-ray Spectroscopy (EDS) coupled to Scanning Electron Microscopy (SEM).