Mass Spectrometric Characterization of Methylaluminoxane

Abstract

Electrospray ionization mass spectrometric studies of poly(methylaluminoxane) (MAO) in the presence of Cp 2 ZrMe 2 , octamethyltrisiloxane (OMTS), or [Bu 4 N]Cl in fluorobenzene solution are reported. The results concur with the hypothesis that MAO is

Droplet Spray Ionization from a Glass Microscope Slide: Real-Time Monitoring of Ethylene Polymerization

“…Because of poor ion intensity by direct analysis of the catalytically active species in toluene, the mixture was diluted fourfold with acetonitrile to enable the acquisition of stable mass spectra 16 containing four cationic species: ion 2 (m/z 235), ion 3 (m/z 255), 2·MeCN (m/z 276) and 3·MeCN (m/z 296) (see Figure 2a). These or similar species have been observed by ESI-MS previously, [14][15][16][17][18] and were easily identified by CID (see Figure S3 in the Supporting Information) and by their isotopic patterns. Cp 2 ZrCl 2 /MAO mixtures are known to be air-sensitive, and Cp 2 ZrOH, m/z 237, overlaps with 2 (m/z 235) and distorts its isotope profile.…”

“…Although this reaction system is quite complicated and still under debate, this catalytic mixture has been the subject of much inquiry, 10-13 including a few in-depth mass spectrometry studies. [14][15][16][17][18] The generally accepted mechanism is shown in Scheme 1. The ligand-exchange reaction of 1 with MAO, in excess, rapidly leads to the catalytically active species 2.…”

NMR and EPR trapping of the active species in the ethylene polymerization and trimerization catalyst systems

“…However, Ti II species were not observed spectroscopically in the catalyst system 11-Me/B(C 6 F 5 ) 3 .…”

“…This tendency supports stable interest to the detailed mechanistic studies of metallocene and post-metallocene catalyzed polymerization [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. However, quite often the available information on the reaction mechanism remains insufficient.…”

“…This was the first example of spectroscopic characterization of intermediates formed in the catalyst systems based on vanadium (III) complexes. In the third system, (FI)TiCl 3 …”