Modifying Methylalumoxane via Alkyl Exchange




Zijlstra, Harmen S.
Joshi, Anuj
Linnolahti, Mikko
Collins, Scott
McIndoe, J. Scott

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Dalton Transactions


Methylalumoxane (MAO) ionizes highly selectively in the presence of octamethyltrisiloxane (OMTS) to generate [Me2Al∙OMTS]+ [(MeAlO)16(Me3Al)6Me]–. We can take advantage of this transformation to examine the reactivity of a key component of MAO using electrospray ionization mass spectrometry (ESI-MS), and here we describe the reactivity of this pair of ions with other trialkyl aluminum (R3Al) components. Using continuous injection methods, we found Et3Al to exchange much faster and extensively at room temperature in fluorobenzene (t½ ~ 2 sec, up to 25 exchanges of Me for Et) than iBu3Al (t½ ~ 40 sec, up to 11 exchanges) or Oct3Al (t½ ~ 200 sec, up to 7 exchanges). The exchanges are reversible and the methyl groups on the cation are also observed to exchange with the added R3Al species. These results point to the reactive components of MAO having a structure that deviates significantly from the cage-like motifs studied to date.



Methylalumoxane, Activators, Aluminum Alkyls, Mass Spectrometry, Homogeneous Catalysis


Zijlstra, H.S., Joshi, A., Linnolahti, M., Collins, S. & McIndoe, J.S. (2018). Modifying Methylalumoxane via Alkyl Exchange. Dalton Transactions, 0(0), xx.