<p>The catalyst [Cp<sub>2</sub>Zr(<i>μ</i>-Me)<sub>2</sub>AlMe<sub>2</sub>]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup>
(<b>1</b>) has been studied by electrospray
ionisation mass spectrometry (ESI-MS) in order to better understand the
complexities of catalyst deactivation in the polymerisation of 1-hexene. Using
offline, online and flow-based methods, we observe that zirconium π-allyl species
are unstable in solution and previously unobserved dimethylalane complexes are
more stable. The dimethylalane complexes are resistant to further 1-hexene
additions and their formation represent a new pathway for catalyst
deactivation.</p>