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

• Published in: Organometallics 2002-09, Vol.21 (20), p.4159-4168
• Main Authors: Metz, Matthew V, Schwartz, David J, Stern, Charlotte L, Marks, Tobin J, Nickias, Peter N
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om020079b

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, C12F8B2(C6F5)2 (8b), are reported. X-ray diffraction analysis of 8b reveals a nearly planar C12F8B2 core with −C6F5 rings rotated 75° out of the plane, hindering π communication between the pendant −C6F5 substituents and the C12F8B2 core, and thereby enhancing Lewis acidity at the boron centers. Competition equilibration experiments with 8b, B(C6F5)3, and acetonitrile over a wide temperature range demonstrate that 8b is a stronger Lewis acid than B(C6F5)3 by Δ H = +1.4(2) kcal/mol and Δ S = −5.3(1) eu. The diffraction-derived molecular structure of 8b←NCCH3 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(C6F5)3 as the cocatalyst.