Structurally defined ring-opening and insertion of pinacolborane into aluminium-nitrogen bonds of sterically demanding dialkylaluminium amides

Victoria A. Pollard, Alan R. Kennedy, Ross McLellan, Duncan Ross, Tell Tuttle, Robert E. Mulvey

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Dialkylaluminium amides iBu 2Al(TMP) and iBu 2Al(HMDS) can perform catalytic hydroboration of ketones with pinacolborane to form the expected boronic esters. However, repeating the same reactions stoichiometrically without a ketone leads unexpectedly to ring-opening of pinacolborane and insertion of its open chain into the Al−N(amido) bond. To date there has been limited knowledge on decomposition pathways of HBpin despite its prominent role in hydroboration chemistry. X-ray crystallography shows these mixed Al−B products [iBu 2Al{OC(Me) 2C(Me) 2O}B(H)(NR 2)] 2 (NR 2=TMP or HMDS) form dimers with an (AlO) 2 core and terminal B−N bonds. Since the bond retention (B−H) and bond breaking (B−O) in these transformations seemed surprising, DFT calculations run using M11/6-31G(d,p) gave an energy profile consistent with a σ-bond metathesis mechanism where London dispersion interactions between iBu and (amide) Me groups play an important stabilising role in the final outcome.

Original languageEnglish
Pages (from-to)50-53
Number of pages4
JournalEuropean Journal of Inorganic Chemistry
Issue number1
Early online date30 Oct 2020
Publication statusPublished - 8 Jan 2021


  • aluminium
  • DFT caluclations
  • homogeneous catalysis
  • hydrocarbons

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