New Perfluoroarylborane Activators for Single-Site Olefin Polymerization. Acidity and Cocatalytic Properties of a “Superacidic” Perfluorodiboraanthracene

The synthesis, Lewis acid properties, and single-site olefin polymerization characteristics of catalyst systems utilizing the binuclear organo-Lewis acid cocatalyst 9,10-bis(pentafluorophenyl)-9,10-diboraoctafluoroanthracene, C 12 F 8 B 2 (C 6 F 5 ) 2 ( 8b ), are reported. X-ray diffraction analysis of 8b reveals a nearly planar C 12 F 8 B 2 core with −C 6 F 5 rings rotated 75° out of the plane, hindering π communication between the pendant −C 6 F 5 substituents and the C 12 F 8 B 2 core, and thereby enhancing Lewis acidity at the boron centers. Competition equilibration experiments with 8b, B(C 6 F 5 ) 3, and acetonitrile over a wide temperature range demonstrate that 8b is a stronger Lewis acid than B(C 6 F 5 ) 3 by Δ H = +1.4(2) kcal/mol and Δ S = −5.3(1) eu. The diffraction-derived molecular structure of 8b ←NCCH 3 reveals substantial skeletal reorganization only at the coordinated boron center. When it is paired with dimethyl organo-group 4 catalyst precursors, 8b affords extremely efficient single-site olefin polymerization systems in both laboratory and large-scale reactors. In all cases, 8b forms polymerization systems with higher activities than those utilizing B(C 6 F 5 ) 3 as the cocatalyst.