V-51 NMR study VOCl3 immobilized on the SiO2 and MgCl2 surface

The magnetic shielding tensor and quadrupole interaction parameters, as wel l as the mutual orientation of tensors for the (equivalent to SiO)VOCl2 com plex obtained by the immobilization of VOCl3 on the SiO2 surface are determ ined. The state of VOCl3 on the surfaces of MgCl2 and modified SiO2 with al l surface OH groups replaced by Cl atoms is studied. To prepare the modifie d SiO2, CCl4 and SiCl4 are used as chlorinating agents. The formation of st ructurally similar pentavalent vanadium complexes on the surface of these s upports is shown. A model for the coordination environment of vanadium on t he chlorine-containing supports is proposed. The vanadium atom exists in th e distorted pentahedral environment and is bound to the support through eit her two chlorine atoms or chlorine and oxygen atoms. A correlation between the coordination of VOCl3 and catalytic properties of VOCl3/MgCl2 is assume d.