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The synthesis and dialkyl abstraction chemistry as well as the unusual cocatalytic characteristics in metallocene-mediated polymerization of two distinctive borane and aluminate cocatalysts tris(2,2‘,2‘‘-nonafluorobiphenyl)borane (PBB) and triphenyl carbenium tris(2,2‘,2‘‘-nonafluorobiphenyl)fluoroaluminate, (Ph3C+PBA-) are reported. Reaction of PBB with Cp‘2ThMe2 (Cp‘ = η5-C5Me5), CGCZrMe2 (CGC = Me2Si(η5-Me4C5)( t BuN)), and Cp‘MMe3 (M = Zr, Hf) cleanly affords base-free cationic complexes Cp‘2ThMe+MePBB- (1), CGCZrMe+MePBB- (5), and Cp‘MMe2 +MePBB- (M = Zr, 7; Hf, 8). In case of CGCTiMe2 and dimethyl zirconocenes, μ-methyl dinuclear cationic complexes [(CGCTiMe)2(μ-Me)]+MePBB- (6) and [(L2ZrMe)2(μ-Me)]+MePBB- (L = η5-C5H5 (Cp), 2; η5-1,2-Me2C5H3 (Cp‘‘), 3; Cp‘, 4; L2 = Me2Si(Ind)2, Ind = η5-C9H6, 9; L2 = Me2C(Flu)(Cp), Flu = η5-C13H8, 10) are formed. A similar reaction with Ph3C+PBA- results in the corresponding complexes CGCZrCH3 +PBA- (M = Zr, 19; Ti, 20) and L2ZrCH3 +PBA- (L = Cp, 15b; Cp‘‘, 16; η5-1,3-(SiMe2)2C5H3, 17; Cp‘, 18; L2 = Me2Si(Ind)2, 21; L2 = Me2C(Flu)(Cp), 22). Two dinuclear complexes 3 and 13 ([Me2C(Flu)(Cp)Zr(C6F5)]2(μ-F)+MeB(C6F5)3 -) derived from borane PBB and B(C6F5)3, respectively, and three other PBA--based monomeric complexes 14 (Ph3C+PBA-), 19, and 21 have been characterized by X-ray diffraction, and these determinations allow detailed analysis of the ion pairing in the solid state. In combination with solution dynamic NMR, all data indicate MePBB-−cation interactions to be considerably weaker than those involving MeB(C6F5)3 -, while the strongly ion-paired chiral PBA- converts previously enantiomeric cations into pairs of diastereomers. As revealed by dynamic 1H NMR studies, ion pair reorganization/symmetrization in 5 is significantly more rapid than in the MeB(C6F5)3 - analogue, suggesting much looser ion pairing in 5. On the other hand, PBA- racemization is a rapid process (e.g., ΔG ‡(58 °C) = 16.9(2) kcal/mol for 16), while cation−PBA- ion pairs have higher barriers for ion pair symmetrization than in analogous fluoroaryl borates. Dinuclear complexes 2 and 3 initiate efficient polymerization of methyl methacrylate (MMA) to produce syndiotactic poly(methyl methacrylate) (PMMA), while 9 produces highly isotactic PMMA, and sterically more accessible complexes 6 and 10 exhibit no activity. For olefin polymerization and copolymerization, PBB-derived cationic complexes, both monomeric and dinuclear, generally exhibit higher catalytic activity and comonomer incorporation levels than the MeB(C6F5)3 - analogues, with CGC catalysts exhibiting the greatest activity contrasts. On the other hand, PBA--derived complexes exhibit a remarkable sensitivity of olefin polymerization characteristics and ion pairing to ancillary ligand bulk, with activity differences of up to 106-fold observed. In regard to stereospecific polymerization, PBA--derived chiral complex 21 produces highly isotactic polypropylene while B(C6F5)4 --derived analogue produces isotactic polypropylene with lower i...

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C(2)-symmetric bis(oxazolinato)lanthanide complexes of the type [(4R,5S)-Ph(2)Box]La[N(TMS)(2)](2), [(4S,5R)-Ar(2)Box]La[N(TMS)(2)](2), and [(4S)-Ph-5,5-Me(2)Box]La[N(TMS)(2)](2) (Box = 2,2'-bis(2-oxazoline)methylenyl; Ar = 4-tert-butylphenyl, 1-naphthyl; TMS = SiMe(3)) serve as precatalysts for the efficient enantioselective intramolecular hydroamination/cyclization of aminoalkenes and aminodienes. These new catalyst systems are conveniently generated in situ from the known metal precursors Ln[N(TMS)(2)](3) or Ln[CH(TMS)(2)](3) (Ln = La, Nd, Sm, Y, Lu) and 1.2 equiv of commercially available or readily prepared bis(oxazoline) ligands such as (4R,5S)-Ph(2)BoxH, (4S,5R)-Ar(2)BoxH, and (4S)-Ph-5,5-Me(2)BoxH. The X-ray crystal structure of [(4S)-(t)BuBox]Lu[CH(TMS)(2)](2) provides insight into the structure of the in situ generated precatalyst species. Lanthanides having the largest ionic radii exhibit the highest turnover frequencies as well as enantioselectivities. Reaction rates maximize near 1:1 BoxH:Ln ratio (ligand acceleration); however, increasing the ratio to 2:1 BoxH:Ln decreases the reaction rate, while affording enantiomeric excesses similar to the 1:1 BoxH:Ln case. A screening study of bis(oxazoline) ligands reveals that aryl stereodirecting groups at the oxazoline ring 4 position and additional substitution (geminal dimethyl or aryl) at the 5 position are crucial for high turnover frequencies and good enantioselectivities. The optimized precatalyst, in situ generated [(4R,5S)-Ph(2)Box]La[N(TMS)(2)](2), exhibits good rates and enantioselectivities, comparable to or greater than those achieved with chiral C(1)-symmetric organolanthanocene catalysts, even for poorly responsive substrates (up to 67% ee at 23 degrees C). Kinetic studies reveal that hydroamination rates are zero order in [amine substrate] and first order in [catalyst], implicating the same general mechanism for organolanthanide-catalyzed hydroamination/cyclizations (intramolecular turnover-limiting olefin insertion followed by the rapid protonolysis of an Ln-C bond by amine substrate) and implying that the active catalytic species is monomeric.

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