Molecular Understanding of the Formation of Surface Zirconium Hydrides upon Thermal Treatment under Hydrogen of (⋮SiO)Zr(CH2tBu)3 by Using Advanced Solid-State NMR Techniques

The reaction of ([triple bondSiO)Zr(CH(2)tBu)(3)] with H(2) at 150 degrees C 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: ([triple bondSiO)(3)Zr-H] (1a, 70-80%) and ([triple bondSiO)(2)ZrH(2)] (1b, 20-30%) along with silicon hydrides, ([triple bondSiO)(3)SiH] and ([triple bondSiO)(2)SiH(2)]. Their structural identities were identified by (1)H DQ solid-state NMR spectroscopy as well as reactivity studies. These two species react with CO(2) and N(2)O to give, respectively, the corresponding formate ([triple bondSiO)(4-x)Zr(O-C(=O)H)(x)] (2) and hydroxide complexes ([triple bondSiO)(4-x)Zr(OH)(x)] (x = 1 or 2 for 3a and 3b, respectively) as major surface complexes.