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

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...

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Bibliographic Details
Published in:Dalton transactions : an international journal of inorganic chemistry 2015-09, Vol.44 (34), p.15286-15296
Main Authors: Weliange, Nandita M, McGuinness, David S, Gardiner, Michael G, Patel, Jim
Format: Article
Language:English
Subjects:
Aluminium
Conversion
Hydrides
Insertion
Isomerization
Octenes
Olefins
Recycled
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Summary: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.
ISSN:1477-9226
1477-9234
DOI:10.1039/c5dt00955c