Dialkylaluminium amides iBu2Al(TMP) and iBu2Al(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 [iBu2Al{OC(Me)2C(Me)2O}B(H)(NR2)]2 (NR2=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.