Electrospray-ionization mass spectrometric studies of poly(methylaluminoxane) (MAO) in the presence of [Cp2 ZrMe2 ], [Cp2 ZrMe(Cl)], and [Cp2 ZrCl2 ] 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 (Me3 Al)y-z (Me2 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 (Me3 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 [Cp2 ZrCl2 ] when compared with [Cp2 ZrMe2 ]. 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 [Cp2 ZrCl2 ], 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.

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

Mass spectrometric analysis of aluminoxanes is difficult due to their high reactivity, thermal instability, involatility, and propensity to form complex mixtures of oligomers. However, the controlled hydrolysis of fluorobenzene solutions of triisobutylaluminum provides surprisingly simple electrospray ionization mass spectra (ESI-MS), consisting of just two main charged species. The most abundant of these can be characterized as [Al3O3 i Bu4(Al i Bu2H)2(Al i Bu3)]−, using a combination of m/z value, isotope pattern, MS/MS studies, and isotopic labeling.

A simple and efficient synthesis and crystallographic analysis of the partially fluorinated 7:8,9:10-dibenzo-1,2,3,4-tetrafluorotriphenylene, 1, in 59% yield is reported. Compound 1 is a blue luminescent [5]helicene in both solution and the solid state. It spontaneously forms enantiomorphous single crystals from racemic samples and exhibits slipped, face-to-face F...C(pi) contacts within the stacks of molecules.

The highly conjugated title compound, C15H16N2O4S2, exhibits an extended planar configuration. This unusual behavior is the result of the azomethine that adopts the E configuration concomitant with the anti­parallel orientation of the thio­phene units. The nitro­gen‐containing double bond is also ca 0.04 Å shorter than its carbon analogue.