Unearthing a Well-Defined Highly Active Bimetallic W/Ti Precatalyst Anchored on a Single Silica Surface for Metathesis of Propane

Manoja Samantaray, Santosh Giridhar Kavitake, Natalia Sanchez Morlanes, Edy Abou-Hamad, Ali Imad Ali Hamieh, Raju Dey, Jean-Marie Basset

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19 Scopus citations

Abstract

Two compatible organometallic complexes, W(Me)(6) (1) and TiNp4 (2), were successively anchored on a highly dehydroxylated single silica support (SiO2-700) to synthesize the well-defined bimetallic precatalyst [(equivalent to Si-O-)W(Me)(5)(equivalent to Si-O-)Ti(Np)(3)] (4). Precatalyst 4 was characterized at the molecular level using advanced surface organometallic chemistry (SOMC) characterization techniques. The strong autocorrelation observed between methyl of W and Ti in H-1-H-1 multiple-quantum NMR spectra demonstrates that W and Ti species are in close proximity to each other. The bimetallic precatalyst 4, with a turnover number (TON) of 9784, proved to be significantly more efficient than the silica-supported monometallic catalyst [(equivalent to Si-O-)W(Me)(5)] (3), with a TON of 98, for propane metathesis at 150 degrees C in a flow reactor. The dramatic improvement in the activity signifies the cooperativity between Ti and W and indicates that the key step of alkane metathesis (C-H bond activation followed by beta-H elimination) occurs on Ti, followed by olefin metathesis, which occurs on W. We have demonstrated the influence and importance of proximity of Ti to W for achieving such a significantly high activity. This is the first report demonstrating the considerably high activity (TON = 9784) in propane metathesis at moderate temperature (150 degrees C) using a well-defined bimetallic system prepared via the SOMC approach.
Original languageEnglish (US)
Pages (from-to)3522-3527
Number of pages6
JournalJournal of the American Chemical Society
Volume139
Issue number9
DOIs
StatePublished - Feb 23 2017

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