Silica-Grafted Borato Cocatalysts for Olefin Polymerization Modeled by Silsesquioxane−Borato Complexes

Abstract

The syntheses and reactivity studies of silsesquioxane-borato complexes are described. Treatment of B(C 6 F 5 ) 3 with (c-C 5 H 9 ) 7 Si 8 O 12 (OH) and (c-C 5 H 9 ) 7 Si 7 O 9 (OH) 3 in the presence of a Brønsted base yields the silsesquioxane-borates, respectively. When the more nucleophilic base pyridine is used, (C 6 F 5 ) 3 B‚NC 5 H 5 (3) is formed instead, demonstrating the competition between B(C 6 F 5 ) 3 and H + to react with the amine. The dimethylaniline in 1a and 2a is readily exchanged by NEt 3 to form 1b and 2b. With the nucleophilic Lewis base NC 5 H 5 , the B-O bond in 1a and 2a is split, yielding (C 6 F 5 ) 3 B‚NC 5 H 5 (3) and the free silsesquioxanes. Complexes 1 and 2 rapidly undergo hydrolysis under formation of the hydroxyl complexes X + {(C 6 F 5 ) 3 BOH} -(4a, X + ) PhN(H)Me 2 + ; 4b, X + ) Et 3 NH + ). Likewise, alcoholysis of 1a and 2a with i-PrOH yields the alkoxide {PhN(H)Me 2 } + {i-PrOB(C 6 F 5 ) 3 } -(5). The B-O bond is only moderately stable toward early-transition-metal alkyls. Nevertheless, Cp 2 Zr(CH 2 Ph) 2 + 1a and Zr(CH 2 Ph) 4 + 2a form single-site ethylene polymerization catalysts. Detailed reactivity studies demonstrated that both B-O and B-C bond splitting plays a crucial role, as not 1a and 2a, but their decomposition product B(C 6 F 5 ) 3 is the actual cocatalyst. The solid-state structures of 1a and 4b were determined by single-crystal X-ray analysis.

Preparation of Porous Acidic Oxides from Group 13 Element-containing Oligosilsesquioxanes.

“…Several silsesquioxanes containing gallium8), aluminum9)-14), or boron15), 16) have also been synthesized.…”

Homogeneous and Heterogeneous Catalysis: Bridging the Gap Through Surface Organometallic Chemistry

“…The activities obtained in the series of aluminasupported monocyclopentadienyl zirconium complexes have always been higher, whatever the oxide used, than those found for the biscyclopentadienyl analogues ( Table 3). [56,57] OB(C 6 F 5 ) 3 } À (HNMe 2 Ph) þ ] (47), was confirmed with model (47 m) [58] and surface studies. Nevertheless the activity obtained for the best catalyst, [Cp*ZrMe 3 /Al 2 O 3(500) ], remained low by comparison to the level of activity reported for the homogeneous systems.…”

“…Nevertheless the activity obtained for the best catalyst, [Cp*ZrMe 3 /Al 2 O 3(500) ], remained low by comparison to the level of activity reported for the homogeneous systems. As pointed out by Duchateau et al [58] the catalytic activity in these systems could in fact only be a result of the reaction of the excess of B(C 6 F 5 ) 3 with the organometallic complex. [19] 4) it is also possible to introduce an external molecular ™noncoordinating Lewis acid∫ on the neutral grafted complexes so as to produce a ™non-floating∫ cationic species.…”

Preparation of Novel Materials for Catalysts Utilizing Metal-Containing Silsesquioxanes

“…With regard to the group 4 transition metal-containing silsesquioxanes, the catalytic activities for various reactions, i.e. the epoxidation of alkenes [2][3][4][5][6][7][8][9][21][22][23][25][26][27][28] and polymerization of small alkenes [2,3,16,17,[35][36][37][38], have been reported. In the course of our study on the preparation of novel group 4 metal-containing silsesquioxanes, we have successfully synthesized titanocenecontaining silsesquioxanes (2a-c) for the first time (equation 3) [39].…”