Boron tetrakis borate

Figure 11.21 Bis(2,4-dinietho5qq)henalene-l,9-diolato)boron tetrakis 3,5-bis(trifluoromethyl)phenyl borate [256].

Wang [3] polymerized ethylene using boron containing activators tris(penta-fluorophenyl)-borane, (II), and lithium tetrakis(pentafluorophenyl)borate, (III). Using tris(pentafluorophenyl)-borane, (II), with alumoxane, Arriola [4] prepared poly(ethylene-co-propylene) and polypropylene. 

B2N4P4Rh2C aH,20, Rhodium(l), tetrakis-(1 -isocyanobutane)bis[methylenebis-(diphenylphosphine)ldi-, bis[tetraphenylborate(l -)], 21 49 BjNACsoHm, Borate(2-), tris[p.-[(l,2-cy-clohexanedione dioximato)-0 O ]diphenyldi-, iron complex, 21 112 B20,Ci4H2g, Boron, bis-p-(2,2-dimethylpropa-noato-0,0 ),-diethyl-p.-oxo-di-, 22 196 B2S3C2H6, [l0B2]-l,2,4,3,5-Trithiadiborolane, 3,5-dimethyl-, 22 225... 

In addition to MAO, boron compounds based on tris(pentafluorophenyl)boron and its derivatives, typically dimethylanilinium tetrakis(pentafluorophenyl) borate, have been used as cocatalysts for sPS polymerizations (40,41). Although MAO has been used in large molar excesses relative to the titanium complex, the boron compounds may be used in roughly equimolar amounts to the titanium catalyst. The boron cocatalyst reacts with a titanium alkyl species, either by protonation in the case of dimethylanilinium tetrakis(pentafluorophenyl)borate or by alkyl group abstraction in the case of tris(pentafluorophenyl)boron, to generate a titanium cationic species with a borate counterion (74-76). The esr spectral evidence has been reported for these systems, supporting a titanium(III) cationic active species (76). 

The polymerization activity of tris(pentafluorophenyl)boron has been reported to be higher than that of dimethylanilinium tetrakis(pentafluorophenyl) borate with [(CHslsCslTiCCHsla as the catalyst (77). It was proposed that the dimethylaniline coordinates to the active site and decreases the polymerization activity. The use of dimethylanilinium tetrakis(pentafluorophenyl)borate with tri-isobutylaluminum (TIBA) and [(CHslsCslTilCHsla as the catalyst has been reported to jdeld high activity for sPS polymerization (74). 

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