Modifying the reactivity in the homologation of propane by introducing aryloxide ligands on a silica supported zirconium alkyl system

Abstract

Grafting the well-defined molecular complexes [(ArO)Zr(CH₂tBu)₃], 2, and [(ArO)₂Zr(CH₂tBu)₂], 3, on SiO_2-(700) (ArO = 2,6-Ph₂C₆H₃O) gives the corresponding monosiloxy surface complexes [(≡SiO)Zr(CH₂tBu)₂(OAr)] and [(≡SiO)Zr(CH₂tBu)(OAr)₂] as major surface species as evidenced by mass balance analysis, IR and NMR spectroscopies. In both cases, minor cyclometallated species (ca. 20%) are also probably formed during the grafting process. While 2/SiO_2-(700) catalytically transforms propane into its lower and higher homologues, 3/SiO_2-(700) remains inactive. Moreover, the formation of butane as the major higher homologues is consistent with the formation of metallocarbene intermediates in this system in contrast to what was observed for the corresponding homologation reaction on silica supported zirconium hydrides.