Diversity in Weakly Coordinating Anions. Mono- and Polynuclear Halo(perfluoroaryl)metalates as Cocatalysts for Stereospecific Olefin Polymerization: Synthesis, Structure, and Reactivity

A series of mononuclear and polynuclear trityl (perfluoroaryl)borate, -aluminate, and -gallate reagents,
potential cocatalysts/activators for metallocene-mediated olefin polymerization, have been synthesized
via fluoride abstraction from trityl fluoride (Ph3CF) by the organo Lewis acid reagents B(C6F5)3 (1),
B(o-C6F5C6F4)3 (2), and Al(C6F5)3 (3), by derivatization of Ph3C+FAl(o-C6F5C6F4)3- (4), and by reaction
of trityl fluoride with in situ generated Ga(C6F5)3 (5). Reaction of trityl fluoride with the tris(perfluoroaryl)boranes 1 and 2 yields the trityl tris(perfluoroaryl)fluoroborates Ph3C+FB(C6F5)3- (6) and Ph3C+FB(o-C6F5C6F4)3- (7), respectively. The three trityl tris(perfluorophenyl)fluoroaluminates (Ph3C+)xFx[Al(C6F5)3]yx-
(x = 1, y = 1, 8; x = 1, y = 2, 9; x = 2, y = 3, 10) can be isolated from the reaction of trityl fluoride
with the tris(perfluoroaryl)alane 3 in the appropriate molar ratios. Reaction of the trityl tris(perfluoroaryl)fluoroaluminate 4 with 3 affords the asymmetric fluoro-bridged trityl bis[tris(perfluoroaryl)]aluminate
Ph3C+(C6F5)3AlFAl(o-C6F5C6F4)3- (11), while reaction of the trityl halides Ph3CCl and Ph3CBr with 3
gives the corresponding trityl tris(perfluorophenyl)haloaluminates Ph3C+XAl(C6F5)3- (X = Cl, 12; X =
Br, 13). The isolable, symmetric fluoro-bridged trityl bis[tris(perfluoroaryl)]gallate Ph3C+F[Ga(C6F5)3]2-
(14) is derived from a “one-pot” reaction of trityl fluoride with Ga(C6F5)3, generated in situ from 4 +
Ga(CH3)3. Of these new species, compounds 7 and 10−14 were characterized by single-crystal X-ray
diffraction. Trityl salts 6−13 react with the Cs-symmetric metallocene precatalyst Me2C(Cp)(Flu)ZrMe2
(15:  Cp = C5H4; Flu = C13H8, fluorenyl) to form isolable ion-pair complexes or characterizable mixtures.
Species 6 reacts with 15 to generate the known ion pair Me2C(Cp)(Flu)ZrMe+MeB(C6F5)3- (16), and
reaction of 7 with 15 gives the fluoro-bridged dimeric diastereomers [Me2C(Cp)(Flu)ZrMe]2(μ-F)+FB(o-C6F5C6F4)3- (17). The trityl tris(perfluorophenyl)fluoroaluminates 8−10 all react with 15 to afford
mixtures of Me2C(Cp)(Flu)ZrMe+FAl(C6F5)3- (18) and diastereomeric [Me2C(Cp)(Flu)ZrMe]2(μ-Me)+(C6F5)3AlFAl(C6F5)3- (19). Asymmetric species 11 cleanly affords the diastereomeric [Me2C(Cp)(Flu)ZrMe]2(μ-Me)+(C6F5)3AlFAl(o-C6F5C6F4)3- (20) in reaction with the metallocene 15. Adducts of 12 and
13 with the metallocene 15 afford the decomposition products Me2C(Cp)(Flu)ZrCl(C6F5) (21) and [Me2C(Cp)(Flu)Zr(μ2-Br)]22+[Al(C6F5)4-]2 (22), respectively. Complexes 17−22 were characterized by single-crystal X-ray diffraction.