86803-85-2

Upstream product

• 128-37-0 2,6-di-tert-butyl-4-methyl-phenol 
• 75-24-1 trimethylaluminum 
• 56252-55-2 bis(2,6-di-tert-butyl-4-methylphenoxide)methylaluminum 
• 41866-82-4 2,6-di-t-butyl-4-methylphenol anionic form 

Relevant academic research and scientific papers

Extraction of Reliable Molecular Information from Diffusion NMR Spectroscopy: Hydrodynamic Volume or Molecular Mass?

Measuring accurate translational self-diffusion coefficients (Dt) by NMR techniques with modern spectrometers has become rather routine. In contrast, the derivation of reliable molecular information therefrom still remains a nontrivial task. In this paper, two established approaches to estimating molecular size in terms of hydrodynamic volume (VH) or molecular weight (M) are compared. Ad hoc designed experiments allowed the critical aspects of their application to be explored by translating relatively complex theoretical principles into practical take-home messages. For instance, comparing the Dt values of three isosteric Cp2MCl2 complexes (Cp=cyclopentadienyl, M=Ti, Zr, Hf), having significantly different molecular mass, provided an empirical demonstration that VH is the critical molecular property affecting Dt. This central concept served to clarify the assumptions behind the derivation of Dt=?(M) power laws from the Stokes–Einstein equation. Some pitfalls in establishing log (Dt) versus log (M) linear correlations for a set of species have been highlighted by further investigations of selected examples. The effectiveness of the Stokes–Einstein equation itself in describing the aggregation or polymerization of differently shaped species has been explored by comparing, for example, a ball-shaped silsesquioxane cage with its cigar-like dimeric form, or styrene with polystyrene macromolecules.

Sterically hindered aluminum alky is: Weakly interacting scavenging agents of use in olefin polymerization

Statically hindered aluminum methyl compounds derived from reaction of hindered phenols with AlMe3 (i.e., MeAl(BHT)2 and MeAl(BHT*)2; BHT = 2,6-di-te>t-butyl-4-methylphenoxide; BHT* = 2,4,6-triterf-butylphenoxide) are useful scavenging agents in olefin polymerization using metallocene catalysts. They do not, or only slowly, react with activators such as B(C6F5)3 or [Ph3C][B(C6F5)4] at 25 °C, nor do they coordinate to or react with metallocenium ion-pairs derived from metallocene dialkyls and these activators. A mixture of AlMe3 and a large excess of MeAl(BHT)2 proves advantageous for catalysts that are susceptible to reaction with BHT-H, the hydrolysis product of MeAl(BHT) 2. Ethylene polymerization experiments establish that the activity of [Cp2ZrMe][MeB(C6F5)3] is only slightly inhibited by AlMe3 in the presence of a significant excess of MeAl(BHT)2. Spectroscopic studies have revealed that AlMe 3 is in equilibrium with MeAl(BHT)2, forming Me 2Al(BHT). At low temperature using 13C NMR spectroscopy, a 1:1 mixture of AlMe3 and MeAl(BHT)2 is shown to consist of Al2Me6, MeAl(BHT)2, and primarily Me 2Al(M-BHT)2AlMe2. A higher temperature, both intra- and intermolecular exchange of both Al-Me and Al-BHT groups, coupled with the temperature dependence of the various equilibria involved, lead to 1H and 13C NMR spectra that are consistent with monomeric Me2Al(BHT). 1H and 19F NMR spectroscopic studies of mixtures of the ion-pairs [Me2C(Cp)IndMMe][MeB(C 6Fs)3] (M = Zr, Hf) or [Me2SiCp 2ZrMe][MeB(C6F5)3] with various quantities of AlMes in the presence of MeAl(BHT)2 were conducted. The AlMe3-mediated degradation of ion-pairs that are susceptible to B(CeF5)3 dissociation is largely absent in the presence of excess MeAl(BHT)2, although reversible formation of [Me 2SiCp2Zr(μ-Me)2AlMe2][MeB(C 6F5)3] and related adducts is observed at low ratios of MeAl(BHT)2 to AlMe3.

Sterically crowded aryloxide compounds of aluminum

The interaction of AlMe3 with 2 equiv of the sterically hindered phenol 2,6-di-tert-butyl-4-methylphenol (BHT-H) gives the disubstituted compound AlMe(BHT)2 (1), whereas the use of an excess of AlMe3 leads to the compound