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Issue 2, 2016

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

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Abstract

The well-defined single-site silica-supported tungsten complex [([triple bond, length as m-dash]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 [([triple bond, length as m-dash]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 [([triple bond, length as m-dash]Si–O–)WH3([double bond, length as m-dash]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.

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

Supplementary files

Article information


Submitted
16 Sep 2015
Accepted
25 Nov 2015
First published
30 Nov 2015

This article is Open Access
All publication charges for this article have been paid for by the Royal Society of Chemistry

Chem. Sci., 2016,7, 1558-1568
Article type
Edge Article

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

N. Maity, S. Barman, E. Callens, M. K. Samantaray, E. Abou-Hamad, Y. Minenkov, V. D'Elia, A. S. Hoffman, C. M. Widdifield, L. Cavallo, B. C. Gates and J. Basset, Chem. Sci., 2016, 7, 1558 DOI: 10.1039/C5SC03490F

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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