Molecular understanding of the formation of surface zirconium Hydrides upon thermal treatment under hydrogen of [( SiO)Zr(CH(2)tBU)(3)] by using advanced solid-state NMR techniques

The reaction of [(dropSiO)Zr(CH(2)tBu)(3)] with H-2 at 150 degreesC leads to the hydrogenolysis of the zirconium-carbon bonds to form a very reactive hydride intermediate(s), which further reacts with the surrounding siloxane ligands present at the surface of this support to form mainly two different zirconium hydrides: [(dropSiO)(3)Zr-H] (1a, 70-80%) and [(dropSiO)(2)ZrH2] (1b, 20-30%) along with silicon hydrides, [(dropSiO)(3)SiH] and [(dropSiO)(2)SiH2]. Their structural identities were identified by H-1 DQ solid-state NMR spectroscopy as well as reactivity studies. These two species react with CO2 and N2O to give, respectively, the corresponding formate [(dropSiO)(4-x)Zr(O-C(=O)H)(x)] (2) and hydroxide complexes [(dropSiO)(4-x)Zr(OH)(x)] (x = 1 or 2 for 3a and 3b, respectively) as major surface complexes.