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

Abstract

The reaction of [(⋮SiO)Zr(CH₂tBu)₃] with H₂ at 150 °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: [(⋮SiO)₃Zr−H] (1a, 70−80%) and [(⋮SiO)₂ZrH₂] (1b, 20−30%) along with silicon hydrides, [(⋮SiO)₃SiH] and [(⋮SiO)₂SiH₂]. Their structural identities were identified by ¹H DQ solid-state NMR spectroscopy as well as reactivity studies. These two species react with CO₂ and N₂O to give, respectively, the corresponding formate [(⋮SiO)_4-xZr(O−C(O)H)_x] (2) and hydroxide complexes [(⋮SiO)_4-xZr(OH)_x] (x = 1 or 2 for 3a and 3b, respectively) as major surface complexes.