Silica supported copper nanoparticles prepared via surface organometallic chemistry: active catalysts for the selective hydrogenation of 2,3-dimethylbutadiene

Mesitylcopper reacts with silica to give supported clusters, then reduced to nanoparticles. These catalysts allow the selective hydrogenation of 2,3-dimethylbutadiene to 2,3-dimethyl-1-butene. Materials were characterized in detail.

Controlling the hydrogenolysis of silica-supported tungsten pentamethyl leads to a class of highly electron deficient partially alkylated metal hydrides

Accessing highly electron deficient partially alkylated tungsten hydrides on silica via controlled hydrogenolysis of surface organometallic complex ( Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> Si–O–)W(Me)₅.

The well-defined single-site silica-supported tungsten complex [( Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> Si–O–)W(Me)₅], 1, is an excellent precatalyst for alkane metathesis. The unique structure of 1 allows the synthesis of unprecedented tungsten hydrido methyl surface complexes via a controlled hydrogenolysis. Specifically, in the presence of molecular hydrogen, 1 is quickly transformed at –78 °C into a partially alkylated tungsten hydride, 4, as characterized by ¹H solid-state NMR and IR spectroscopies. Species 4, upon warming to 150 °C, displays the highest catalytic activity for propane metathesis yet reported. DFT calculations using model systems support the formation of [( Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> Si–O–)WH₃(Me)₂], as the predominant species at –78 °C following several elementary steps of hydrogen addition (by σ-bond metathesis or α-hydrogen transfer). Rearrangement of 4 occuring between –78 °C and room temperature leads to the formation of an unique methylidene tungsten hydride [( Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> Si–O–)WH₃( Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CH₂)], as determined by solid-state ¹H and ¹³C NMR spectroscopies and supported by DFT. Thus for the first time, a coordination sphere that incorporates both carbene and hydride functionalities has been observed.