Characterization of Isobutylaluminoxanes by Electrospray Ionization Mass Spectrometry

Henderson, Matthew A.; Trefz, Tyler; Collins, Scott; Wang, Miles Y.; McIndoe, J. Scott

doi:10.1021/om3010977

Cited by 34 publications

(45 citation statements)

References 50 publications

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“…Adding two AlOMe units to a single square face of (AlOMe) 6 yields (AlOMe) 8 , and subsequent growth in onedimension results in the nanotubes 35,41 shown in Figure 4. Because of this the six-mer and eight-mer can be thought of as the smallest nanotubes.…”

Section: Resultsmentioning

confidence: 99%

The Dynamic Equilibrium Between (AlOMe)_n Cages and (AlOMe)_n·(AlMe₃)_m Nanotubes in Methylaluminoxane (MAO): A First-Principles Investigation

2014

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Species likely to be present in methylaluminoxane (MAO) are studied via dispersion-corrected DFT, which we show is able to accurately predict thermochemical parameters for the dimerization of trimethylaluminum (TMA). Both cage-like, (AlOMe) n,c , and TMA-bound nanotubes, (AlOMe) n,t ·(AlMe 3 ) m , are found to be important components of MAO. The most stable structures have aluminum/oxygen atoms in environments whose average hybridization approaches sp 3 /sp 2 . The (AlOMe) n,t ·(AlMe 3 ) m isomers with the lowest free energies possess Al−μ-Me−Al bonds. At 298 K a novel T d -(AlOMe) 16,c oligomer is one of the most stable structures among the six stoichiometries with the lowest free energies: (AlOMe) 20,c ·(AlMe 3 ) 2 , T d -(AlOMe) 16,c , (AlOMe) 18,c , (AlOMe) 20,c ·(AlMe 3 ), (AlOMe) 10,t ·(AlMe 3 ) 4 , and (AlOMe) 20,c . As the temperature rises, the abundance of (AlOMe) n,t ·(AlMe 3 ) m decreases, and that of (AlOMe) n,c increases. Because the former are expected to be precursors for the active species in polymerization, this may in part be the reason why the cocatalytic activity of MAO decreases at higher temperatures.

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Section: Resultsmentioning

confidence: 99%

The Dynamic Equilibrium Between (AlOMe)_n Cages and (AlOMe)_n·(AlMe₃)_m Nanotubes in Methylaluminoxane (MAO): A First-Principles Investigation

2014

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“…[6,7] Moreover,gas-phase fragmentation experiments on the mass-selected ions provide unique information on their microscopicr eactivity. Under carefully optimized conditions, ESI mass spectrometry can detects ensitive organometallic ate complexes in their intact form.…”

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confidence: 99%

Ate Complexes in Iron‐Catalyzed Cross‐Coupling Reactions

Parchomyk

Koszinowski

2016

Chemistry A European J

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Iron-catalyzed cross-coupling reactions have an outstanding potential for sustainable organic synthesis, but remain poorly understood mechanistically. Here, we use electrospray-ionization (ESI) mass spectrometry to identify the ionic species formed in these reactions and characterize their reactivity. Transmetalation of Fe(acac) (acac=acetylacetonato) with PhMgCl in THF (tetrahydrofuran) produces anionic iron ate complexes, whose nuclearity (1 to 4 Fe centers) and oxidation states (ranging from -I to +III) crucially depend on the presence of additives or ligands. Upon addition of iPrCl, formation of the heteroleptic Fe complex [Ph Fe(iPr)] is observed. Gas-phase fragmentation of this complex results in reductive elimination and release of the cross-coupling product with high selectivity.

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“…Considering alkylalumoxane reactions with Ph 2 Si(OH) 2 , we kept in mind that the aluminum atom is four-coordinated in alkylalumoxanes [2,3,4,5,6,7,8,9,10,11,12,13,14,15], whose schematic structural formulas are presented as follows: (at n = 1—tetraisobutylalumoxane, at n > 1—polyisobutylalumoxane) [3] (Figure 3). …”

Section: Resultsmentioning

confidence: 99%

“…Since the beginning of the 1990s, detailed studies of the synthesis, properties, and structure of alkylalumoxanes have been carried out [7,8,9,10,11,12,13,14]. In 2013, works on this problem were summarized in the review [15].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Siloxyalumoxanes and Alumosiloxanes Based on Organosilicon Diols

2017

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We have drawn a few interesting conclusions while studying reaction products of Ph2Si(OH)2 with Al(iBu)3 and tetraisobutylalumoxane. In the first place, this is the production (at a Ph2Si(OH)2 and Al(iBu)3 equimolar ratio) of an oligomer siloxyalumoxane structure with alternating four- and six-member rings. In addition, it shows isobutyl and phenyl group migration between aluminum and silicon due to the formation of an intramolecular four-member cyclic complex [Ph2(OH)SiO]Al(iBu)2 → [(iBu)Ph(OH)SiO]Al(iBu)Ph. Ph2Si(OH)2 interaction with Al(iBu)3 not only starts from intramolecular complex production, but the chain is terminated for the same reason, which in the case of the Ph2Si(OH)2 reaction with tetraisobutylalumoxane results in failure of to obtain high-polymer siloxyalumoxane compounds. When Al(iBu)3 interacts with α- and γ-diols, no oligomer compounds are produced. In the Al(iBu)3 reaction with α, γ-diols are created in monomer compounds that are likely to have a cyclic structure. Notably, when Al(iBu)3 interacts with only α-diol, a double excess of Al(iBu)3 allows for full replacement of hydrogen in the α-diol hydroxyl groups by aluminum alkyl residue with 1,3-bis(diisobutylalumoxymethyl)-1,1,3,3-tetramethyldisiloxane production. At an equimolar ratio of initial reagents, the second isobutyl radical at Al does not interact with the second hydroxyl group of α-diol, apparently due to the steric hindrance, and 1-(diisobutylalumoxymethyl)-3-(hydroxymethyl)-1,1,3,3-tetramethyl-disiloxane is produced. Al(iBu)3 reactions with γ-diol also result in monomer compounds, but the presence of a chain consisting of three CH2-groups between Si and the hydroxyl group facilitates interaction between the second hydroxyl group of γ-diol and the second isobutyl radical Al(iBu)3. Tetraisobutylalumoxane reactions with α- and γ-diols result in oligomer compounds.

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Characterization of Isobutylaluminoxanes by Electrospray Ionization Mass Spectrometry

Cited by 34 publications

References 50 publications

The Dynamic Equilibrium Between (AlOMe)_n Cages and (AlOMe)_n·(AlMe₃)_m Nanotubes in Methylaluminoxane (MAO): A First-Principles Investigation

The Dynamic Equilibrium Between (AlOMe)_n Cages and (AlOMe)_n·(AlMe₃)_m Nanotubes in Methylaluminoxane (MAO): A First-Principles Investigation

Ate Complexes in Iron‐Catalyzed Cross‐Coupling Reactions

Synthesis of Siloxyalumoxanes and Alumosiloxanes Based on Organosilicon Diols

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Characterization of Isobutylaluminoxanes by Electrospray Ionization Mass Spectrometry

Cited by 34 publications

References 50 publications

The Dynamic Equilibrium Between (AlOMe)n Cages and (AlOMe)n·(AlMe3)m Nanotubes in Methylaluminoxane (MAO): A First-Principles Investigation

The Dynamic Equilibrium Between (AlOMe)n Cages and (AlOMe)n·(AlMe3)m Nanotubes in Methylaluminoxane (MAO): A First-Principles Investigation

Ate Complexes in Iron‐Catalyzed Cross‐Coupling Reactions

Synthesis of Siloxyalumoxanes and Alumosiloxanes Based on Organosilicon Diols

Contact Info

Product

Resources

About

The Dynamic Equilibrium Between (AlOMe)_n Cages and (AlOMe)_n·(AlMe₃)_m Nanotubes in Methylaluminoxane (MAO): A First-Principles Investigation

The Dynamic Equilibrium Between (AlOMe)_n Cages and (AlOMe)_n·(AlMe₃)_m Nanotubes in Methylaluminoxane (MAO): A First-Principles Investigation