Issue 34, 2015

Insertion, elimination and isomerisation of olefins at alkylaluminium hydride: an experimental and theoretical study

Abstract

The insertion, elimination and isomerisation of octenes with di-n-octylaluminium hydride [HAl(Oct)2], tri-n-octylaluminium [Al(Oct)3] and sec-octylaluminium species have been studied as individual steps in a putative aluminium based contrathermodynamic olefin isomerisation process. While elimination of 1-octene from [Al(Oct)3] is energetically unfavourable, the process is driven by high temperature vacuum distillation, leading to very high selectivity to 1-octene (>97%). At high conversions the [HAl(Oct)2] so obtained exists predominately as hydride-bridged cyclic oligomers, whereas at low conversion the mixed alkyl/hydride-bridged dimer [(Oct)2Al(μ-H)(μ-Oct)Al(Oct)2] is the major species. Di-n-octylaluminium hydride recovered after olefin elimination may be recycled and is active toward re-insertion of octenes. Internal octenes (cis- and trans-2-, 3- and 4-octene) only partially insert however, and even after prolonged heating there is no significant secondary to primary alkyl isomerisation evident.

Graphical abstract: Insertion, elimination and isomerisation of olefins at alkylaluminium hydride: an experimental and theoretical study

Supplementary files

Article information

Article type
Paper
Submitted
10 Mar 2015
Accepted
27 May 2015
First published
29 May 2015

Dalton Trans., 2015,44, 15286-15296

Author version available

Insertion, elimination and isomerisation of olefins at alkylaluminium hydride: an experimental and theoretical study

N. M. Weliange, D. S. McGuinness, M. G. Gardiner and J. Patel, Dalton Trans., 2015, 44, 15286 DOI: 10.1039/C5DT00955C

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