Continuous-Flow Alkane Dehydrogenation by Supported Pincer-Ligated Iridium Catalysts at Elevated Temperatures

Boris Sheludko, Molly T. Cunningham, Alan S Goldman, Fuat E. Celik

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Pincer-ligated iridium complexes of the form [Ir(R4PCP)L] (R4PCP = κ3-C6H3-2,6-(XPR2)2; X = CH2, O; R = tBu, iPr) are efficient homogeneous alkane dehydrogenation catalysts that have been reported to be highly active at temperatures of 240 °C or below. In this work, silica-supported [Ir(C2H4)(p-tBu2PO-tBu4POCOP)] (1/SiO2) was used to study a model continuous-flow gas-phase acceptorless alkane dehydrogenation system. This particular supported framework is thermally stable at temperatures up to 340 °C, 100 °C above the highest temperature at which analogous homogeneous complexes have been reported to show stable activity, with observed butane dehydrogenation rates of ca. 80 molbutenes molcat. -1 h-1. Solid-state 31P MAS NMR and ATR IR are used to demonstrate that the backbone pincer ligand remains intact and coordinated at 340 °C. The complex is fully converted to [Ir(CO)(p-tBu2PO-tBu4POCOP)] (3/SiO2) above 300 °C. 3/SiO2 is observed to be catalytically active at the higher temperatures tested, and reaction rates are comparable to those of 1/SiO2. 3/SiO2 and 1/SiO2 act as resting states for the active 14-electron fragment, through dissociation of the CO or olefin ligand, respectively. Given that 3/SiO2 is air resistant at ambient temperature and is structurally stable and catalytically active at elevated temperatures, it is a suitable candidate as a catalyst for the highly endothermic acceptorless dehydrogenation of alkanes.

Original languageEnglish
Pages (from-to)7828-7841
Number of pages14
JournalACS Catalysis
Volume8
Issue number9
DOIs
Publication statusPublished - Sep 7 2018

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Iridium
Alkanes
Dehydrogenation
Carbon Monoxide
Paraffins
Catalysts
Temperature
Ligands
Butane
Olefins
Reaction rates
Silica
Nuclear magnetic resonance
Alkenes
Silicon Dioxide
Electrons
Air
Gases

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

Cite this

Continuous-Flow Alkane Dehydrogenation by Supported Pincer-Ligated Iridium Catalysts at Elevated Temperatures. / Sheludko, Boris; Cunningham, Molly T.; Goldman, Alan S; Celik, Fuat E.

In: ACS Catalysis, Vol. 8, No. 9, 07.09.2018, p. 7828-7841.

Research output: Contribution to journalArticle

Sheludko, Boris ; Cunningham, Molly T. ; Goldman, Alan S ; Celik, Fuat E. / Continuous-Flow Alkane Dehydrogenation by Supported Pincer-Ligated Iridium Catalysts at Elevated Temperatures. In: ACS Catalysis. 2018 ; Vol. 8, No. 9. pp. 7828-7841.
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