Borane-functionalized oxide supports: development of active supported metallocene catalysts at low aluminoxane loading

Hydrogen Bonding and Lewis Acid–Base Interactions in the System Bis(pentafluorophenyl)borinic Acid / Methanol

“…[19] The other main initial product detected in the low-temperature titrations (Figure 2) was 3c (Scheme 1), in which a MeOH molecule is simultaneously B-bonded and Hbonded within an octanuclear ring. This species is analogous to the species 3a, containing a water molecule instead of MeOH, which spontaneously forms [together with the anhydride Ar 2 BOBAr 2 , [5,20] equation (3a)] whenever dichloromethane solutions of 1 are cooled to temperatures low enough to make the very unfavorable entropy term in equilibrium 3b (see Figure 2a) less important.…”

“…[2] Much of the work focused on tris(pentafluorophenyl)-borane, [3] but related molecules have also been extensively investigated. Among these, bis(pentafluorophenyl)borinic acid (C 6 F 5 ) 2 BOH (1, hereafter borinic acid) [4,5] has been the object of a number of fundamental and applicative studies, [6][7][8][9][10][11] because of its peculiar reactivity. We have previously shown [8] that 1 is a cyclic trimer (1 t , Scheme 1) in the solid state, [12] whilst in solution, complete instability of its adducts with MeOH and thf.…”

Improving the Performance of Heterogeneous Borane Cocatalysts by Pretreatment of the Silica Support with Alkylaluminum Compounds

“…Our system is different than that of Tian et al [6] in that we used zirconocene dichloride (instead of dimethylzirconocene) and our cocatalyst is stabilized on the support by the carbenium ion.…”

“…[6] The reaction mechanism of boranefunctionalized or supported zirconocene on silica is proposed to be as shown in Scheme 1.…”

“…These supported catalysts work very well in ethylene and propylene polymerization with a low loading of alkylaluminum compounds. [6,7] Hlatky and coworkers, and Ward made heterogeneous organoboranes by providing a catalyst activator chemically bound directly to the support. This catalyst system reduced reactor fouling and increased the bulk density of the polymer product.…”