Surface organometallic chemistry of zirconium: Application to the stoichiometric activation of the CH bonds of alkanes and to the low-temperature catalytic hydrogenolysis of alkanes

Tetrakis(neopentyl)zirconium reacts with the surface of silica, dehydroxylated at 773 K, to give the surface tris(neopentyl)zirconium complex, SiOOZrNp₃ (1). Under molecular hydrogen (423 K, 400 torr), 1 is transformed into surface zirconium hydrides (2) and silicon hydrides. Complex 2 activates the CH bonds of cyclooctane and methane via a σ-bond metathesis reaction, and selectively at low temperatures hydrogenolyzes alkanes such as neopentane, isobutane and propane, but not ethane. The mechanism proposed involves, inter alia, the activation of CH bonds of the alkanes and the activation of the CC bond of the alkyl groups via β-methyl migration steps.