Alternately, this ion-pair is in direct equilibrium with Cp2ZrMe2 and MAO and the larger size of the latter species will counter the effect of the third equilibrium. In other studies, discrete contact ion-pairs like 2 were shown to be in equilibrium with σchlorobenzene complexes so it is possible this equilibrium may also reduce the average dimensions of ion-pair 2 as well. So, unfortunately, we are unable to comment on whether the MAO-based, metallocenium ion-pairs are different in a polar vs. non-polar solvent since all we observe is an average. In earlier work using the stronger donor OMTS, we were able to show that the negative ion ESI-MS spectra are similar in PhF compared with toluene, as electrospray experiments are feasible, though not practical in this solvent.48 Evidently, further work appears necessary, especially as these early ESI-MS experiments involved aged MAO.