| The synthesis, Lewis acid characteristics, and Ziegler-Natta single-site olefin polymerization behavior of catalyst systems utilizing the binuclear Lewis acid octafluoro-9,10-bis-pentafluorophenyl-9,10-dihydro-9,10-diboraanthracene, C12F8B2(C6F5)2 ( 8b), are reported. X-ray diffraction analysis of 8b reveals a nearly planar C12F8B2 core with −C 6F5 rings rotated 75° out of the plane, hindering π communication between the pendant −C6F5 substituents and the C12F8B2 core, thus enhancing the Lewis acidity of the boron centers. Competition equilibration experiments of 8b and B(C6F5)3 for acetonitrile measured via 19F NMR over a wide temperature range demonstrate that 8b is a stronger Lewis acid (ΔH = +1.4(2) kcal/mol and ΔS = −5.3(1) eu). When paired with dimethyl metallocene catalyst precursors, extremely efficient single-site olefin polymerization systems are formed in both laboratory and large-scale polymerization reactors.; A new class of cocatalysts for single-site olefin polymerization consisting of perfluorophenoxide ligands and devoid of group 13 elements has been synthesized, characterized, and tested for use as polymerization cocatalysts. The first set of cocatalysts utilized pentafluorophenoxide ligands: Ph3C +Al(OC6F5)4−( 4), Ph3C+M(OC6F5) 6− (M = Nb (6a); M = Ta (6b )). X-ray diffraction analysis of 6 reveals six-coordinate metal centers with substantial distortion of the M-O-C6F5 linkages from linearity. The reactivity and cocatalytic characteristics of 6 were investigated with respect to a series of metallocene dimethyls. For sterically unencumbered metallocenes, facile C6F 5O− transfer from Nb/Ta to Zr/Ti is observed. However, [(C5Me5)2ZrMe(THF-d8)] +Nb(OC6F5)6− (7) is formed in the reaction of 6a with (C 5Me5)2ZrMe2 in THF-d8. In situ activation of (C5Me5)2ZrMe 2 and (C5Me4H)2ZrMe2 with 4 and 6 yields efficient ethylene polymerization catalysts, having activities comparable to those of Ph3C+B(C 6F5)4−. To impede aryloxide ring transfer, a bulkier ligand, 2-nonafluorobiphenoxide (C12F 9O−), was combined with highly oxophilic Y +3 and La+3 centers. Reaction of M[CH(SiMe3) 2]3 (M = Y, La) with 4.0 equiv. 2-HOC12F 9 results in the clean formation of H+M(OC12F 9)4− salts (M = Y (9a); M = La, (9b)) in high yield. When 9 is paired with metallocene dimethyl precursors, even sterically open precatalysts such as CGCTiMe2 (CGC = Me2Si(C5Me4) tBuN) or (C5H5)2ZrMe 2 yield highly active ethylene polymerization systems. |
