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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Henderson, Matthew A. Trefz, Tyler K. Collins, Scott Linnolahti, Mikko Mcindoe, J. Scott |
| Description | Author Affiliation: Trefz TK ( Department of Chemistry, University of Victoria, P.O. Box 3065 Victoria, BC V8W3V6 (Canada).) |
| Abstract | Electrospray-ionization mass spectrometric studies of poly(methylaluminoxane) (MAO) in the presence of $[Cp_{2}ZrMe_{2}],$ $[Cp_{2}ZrMe(Cl)],$ and $[Cp_{2}ZrCl_{2}]$ in fluorobenzene (PhF) solution are reported. The results demonstrate that alkylation and ionization are separate events that occur at competitive rates in a polar solvent. Furthermore, there are significant differences in ion-pair speciation that result from the use of metallocene dichloride complexes in comparison to alkylated precursors at otherwise identical Al/Zr ratios. Finally, the counter anions that form are dependent on the choice of precursor and Al/Zr ratio; halogenated aluminoxane anions $[(MeAlO)_{x}(Me_{3}Al)_{y−z}(Me_{2}AlCl)_{z}Me]^{−}$ (z=1, 2, 3…) are observed using metal chloride complexes and under some conditions may predominate over their non-halogenated precursors $[(MeAlO)_{x}(Me_{3}Al)_{y}Me]^{−}.$ Specifically, this halogenation process appears selective for the anions that form in comparison to the neutral components of MAO. Only at very high Al/Zr ratios is the same “native” anion distribution observed when using $[Cp_{2}ZrCl_{2}]$ when compared with $[Cp_{2}ZrMe_{2}].$ Together, the results suggest that the need for a large excess of MAO when using metallocene dichloride complexes is a reflection of competitive alkylation vs. ionization, the persistence of unreactive, homodinuclear ion pairs in the case of $[Cp_{2}ZrCl_{2}],$ as well as a change in ion pairing resulting from modification of the anions formed at lower Al/Zr ratios. Models for neutral precursors and anions are examined computationally. |
| ISSN | 09476539 |
| e-ISSN | 15213765 |
| Journal | Chemistry - A European Journal |
| Issue Number | 7 |
| Volume Number | 21 |
| Language | English |
| Publisher | Wiley-VCH;ChemPubSoc Europe |
| Publisher Date | 2015-02-09 |
| Publisher Place | Germany |
| Access Restriction | Open |
| Subject Keyword | Chemistry |
| Content Type | Text |
| Resource Type | Article |
| Subject | Organic Chemistry Catalysis |
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