Syndiospecific living polymerization of 4‐methylstyrene and styrene with (trimethyl)pentamethylcyclopentadienyltitanium/tris(pentafluorophenyl)borane/trioctylaluminum catalytic system

The polymerizations of styrene and 4‐methylstyrene (4MS) with a half‐metallocene type catalytic system composed of (trimethyl)pentamethylcyclopentadienyltitanium (Cp*TiMe₃), trioctylaluminum (AlOct₃), and tris(pentafluorophenyl)borane [B(C₆F₅)₃] were investigated at ?25 °C. The addition of AlOct₃ as a third component of the catalytic system is effective both to promote the syndiospecific polymerization and to inhibit the nonstereospecific polymerization at the low‐temperature region. The use of AlOct₃ was also effective to eliminate the chain transfer reaction to alkylaluminum. The number‐average molecular weights (M_n's) of poly(4MS) or polystyrene increased proportionally with increasing monomer conversion. The molecular weight distribution (MWD) of polymer stayed narrow [M_w/M_n = ～ 1.1 for poly(4MS) and M_w/M_n = ～ 1.5 for polystyrene]. It was thus concluded that the polymerizations of the styrenic monomers with Cp*TiMe₃/B(C₆F₅)₃/AlOct₃ catalytic system proceeded under living fashion at ?25 °C. The living random copolymerization behaviors of styrene and 4MS were also confirmed. The ¹³C NMR analysis clarified that each of the homopolymers and random copolymers obtained in this work had highly syndiotactic structure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3692–3706, 2001     

Kinetic study on the living/controlled cationic polymerization of p‐methoxystyrene coinitiated by tris(pentafluorophenyl)borane

A kinetic study of the living cationic polymerization of p‐methoxystyrene using 1‐(4‐methoxyphenyl)ethanol ( 1 )/B(C₆F₅)₃ initiating system in a mixture of CH₃CN with CH₂Cl₂ 1:1 (v/v) at room temperature was carried out utilizing a wide variety of conditions. The polymerization proceeded in a living fashion even in the presence of a large amount of water ([H₂O]/[B(C₆F₅)₃] ratio up to 20) to afford polymers whose M_n increased in direct proportion to monomer conversion with fairly narrow MWDs (M_w/M_n ≤ 1.3). The investigation revealed that the rate of polymerization was first‐order in B(C₆F₅)₃ concentration, while a negative order in H₂O concentration close to ?2 was obtained. It was also found that the rate of polymerization decreased with lowering temperature, which could be attributed to a decreased concentration in free Lewis acid, the true coinitiator of polymerization. A mechanistic scheme to explain the kinetic behavior of living p‐methoxystyrene polymerization is proposed, which has been validated by PREDICI simulation on multiple‐data curves obtained by ¹H NMR in situ polymerization experiment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6928–6939, 2008     

Ring-opening reactions of nonactivated aziridines catalyzed by tris(pentafluorophenyl)borane

The ring-opening reactions of nonactivated aziridines with amine nucleophiles are efficiently catalyzed by tris(pentafluorophenyl)borane leading to derivatives of trans-1,2-diamines in high yields. A mechanistic investigation of the reaction suggests that in situ formed [(C(6)F(5))(3)B(OH(2))].H(2)O catalyzes the opening through a Br?nsted acid manifold.     

Addition polymerization of norbornene using bis(β‐ketoamino)nickel(II)/tris(pentafluorophenyl)borane catalytic systems

Norbornene polymerizations proceeded in toluene with bis(β‐ketoamino)nickel(II) {Ni[CH₃C(O)CHC(NR)CH₃]₂ [R = phenyl ( 1 ) or naphthyl ( 2 )]} complexes as the catalyst precursors and the organo‐Lewis compound tris(pentafluorophenyl)borane [B(C₆F₅)₃] as a unique cocatalyst. The polymerization conditions, such as the cocatalyst/catalyst ratio (B/Ni), catalyst concentration, monomer/catalyst ratio (norbornene/Ni), polymerization temperature, and polymerization time, were studied in detail. Both bis(β‐ketoamino)nickel(II)/B(C₆F₅)₃ catalytic systems showed noticeably high conversions and activities. The polymerization activities were up to 3.64 × 10⁷ g of polymer/mol of Ni h for complex 1 /(B(C₆F₅)₃ and 3.80 × 10⁷ g of polymer/mol of Ni h for complex 2 /B(C₆F₅)₃, and very high conversions of 90–95% were maintained; both polymerizations provided high‐molecular‐weight polynorbornenes with molecular weight distributions (weight‐average molecular weight/number‐average molecular weight) of 2.5–3.0. The achieved polynorbornenes were confirmed to be vinyl‐addition and atactic polymers through the analysis of Fourier transform infrared, ¹H NMR, and ¹³C NMR spectra, and the thermogravimetric analysis results showed that the polynorbornenes exhibited good thermal stability (decomposition temperature > 410 °C). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4733–4743, 2007     

Metal-free catalytic hydrogenation of imines with tris(perfluorophenyl)borane

Metal-free homogeneous catalysed hydrogenation of various imines was accomplished with tris(perfluorophenyl)borane under moderate reaction conditions.     

The structure and chemistry of tris(pentafluorophenyl)borane protected mononuclear nitridotitanium complexes

Treatment of TiCl(NMe(2))(3) with H(3)N·B(C(6)F(5))(3) results in N-H activation and ligand exchange to yield the structurally characterised salt [TiCl(NMe(2))(2)(NMe(2)H)(2)](+)[Ti[triple bond]NB(C(6)F(5))(3)(Cl)(2)(NMe(2)H)(2)](-). Cation exchange with [Me(4)N]Cl, [Ph(4)P]Cl and [(PhCH(2))Ph(3)P]Cl yields the respective ammonium and phosphonium salts of the [Ti[triple bond]NB(C(6)F(5))(3)(Cl)(2)(NMe(2)H)(2)](-) anion. X-ray crystallography reveals that the essential trigonal bipyramidal geometry and composition of the anion is retained in each of these salts despite some minor variations in the Ti-N-B angle and the nature of the interionic interactions. Electronic investigation by DFT calculations confirmed the Ti-N triple bond character implied by the experimentally determined bond length, with the HOMO and HOMO-1 having Ti-N π-bonding character. The dimethylamine ligands of the anion resist substitution by moderate bases but can be displaced by pyridine to give a pentacoordinate anion. In contrast, addition of 2,2'-bipyridyl gives a neutral octahedral complex. Treatment of the pyridine complex with TlCp results in the formation of a four coordinate anionic cyclopentadienyl complex.     

Metal and solvent‐free cyanosilylation of carbonyl compounds with tris(pentafluorophenyl)borane

A highly effective method of the cynaosilylation of aldehydes and ketones with TMSCN in the presence of catalytic amount of B(C₆F₅)₃ [tris(pentafluorophenyl)borane] has been developed. Cyano transfer from TMSCN to carbonyl group proceeds at room temperature under solvent‐free conditions. Various alehydes and ketones have been converted into the corresponding trimethylsilylether within short reaction times with excellent yield under mild conditions. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of tris(pentafluorophenyl)borane on the activation of the Ni(II)-based catalyst in the addition polymerization of norbornene

The activity of the transition metal complex, such as Ni(2-ethyl hexanoate)₂ (1), Co(2-ethyl hexanoate)₂ (2), TiCl₄ (3), or CpTiCl₃ (4) (Cp = cyclopentadiene), in combination with MAO (methylaluminoxane), was investigated in the polymerization of norbornene. The Ni(II) complex 1 with MAO showed moderate activity to give 20.8 kg_polymer/mol_Ni h, while the other three complexes 2-4 with MAO just showed trivial activity. Effects of the Lewis acids on the activation of the catalyst of 1/MAO were examined. The employment of B(C₆F₅)₃ with 1/MAO significantly enhanced the activity to give up to around 133 kg_polymer/mol_Ni h. The use of other borane compounds, such as B(C₆H₅)₃ and BEt₃, or the stronger electron acceptor BF₃ · OBu₂, with 1/MAO in place of B(C₆F₅)₃ clearly showed the main functions of B(C₆F₅)₃. The high Lewis acidity of B(C₆F₅)₃ enabled it to develop matured active complexes, thus enhancing the activity. Several Ni(II) complexes were employed to determine whether their activity was comparable to that of complex 1 in norbornene polymerization. The study of the ¹H and ¹³C NMR spectra of the polynorbornene produced with 1/B(C₆F₅)₃/MAO showed that the initiation of addition polymerization occurred through the insertion of the exo face of the norbornene into the active complex. Effects of the variation in the polymerization variables, such as the levels of B(C₆F₅)₃ and MAO, temperature, and solvent, on the polymerization were discussed.     

Aqueous cationic olefin polymerization using tris(pentafluorophenyl)gallium and aluminum

Tris(pentafluorophenyl)gallium ( 3 ) and aluminum ( 7 ) are active coinitiators for the production of medium‐high molecular weight (MW) polymers of styrene and isobutene (IB) under aqueous reaction conditions. Strong Brønsted acids formed in situ by reaction of these coinitiators with background moisture present in the monomer droplet ( 5 and 8 , respectively) are believed to be responsible for inducing cationic polymerization of these monomers. Of the two, 7 is the most active for IB polymerization in both aqueous media and anhydrous aliphatic solvents. These results are in contradistinction to tris(pentafluorophenyl)boron ( 2 ), which is incapable of polymerizing IB in aqueous or aliphatic media. The MWs of the polyisobutenes (PIBs) produced under aqueous conditions by either coinitiator greatly exceed those formed under similar reaction conditions by the strongly acidic chelating diborane (1,2‐C₆F₄[B(C₆F₅)₂]₂, 1 ) or diborole (1,2‐C₆F₄[9‐BC₁₂F₈]₂, 6 ). Both 3 and 7 are readily synthesized from the corresponding Group 13 halide compounds in conjunction with bis(pentafluorophenyl)zinc ( 4 ). Aqueous polymerization of IB dissolved in aliphatic solvents with 3 or 7 can yield PIBs with relatively narrow polydispersities. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Oxygen-bridged borate anions from tris(pentafluorophenyl)borane: synthesis, NMR characterization, and reactivity

The previously known anion [(C6F5)3B(mu-OH)B(C6F5)3]- (2) has been prepared by a two-step procedure, involving deprotonation of (C6F5)3BOH2 to give [B(C6F5)3OH]- (1), followed by addition of B(C6F5)3. The solution structure and the dynamics of 2 have been investigated by 1H and 19F NMR spectroscopy. The reaction of [NHEt3]2 with NEt3 resulted in the formation of [NHEt3]+ [(C6F5)3BOH]-, [NHEt3]+ [(C6F5)3BH]-, and (C6F5)3B- (CH2CH=N+ Et2). This indicates that in the presence of a nucleophile anion 2 can dissociate to B(C6F5)3 and 1. The reaction of [HDMAN]2 with 1,8-bis(dimethylamino)naphthalene (DMAN) confirmed this trend. In the presence of water, 2 transformed into the adduct [(C6F5)3BO(H)H...O(H)B(C6F5)3]- (3), containing the borate 1 hydrogen-bonded to a water molecule coordinated to B(C6F5)3. The same compound is formed by treating (C6F5)3BOH2 with 0.5 equiv of a base. A competition study established that for 1 the Lewis acid-base interaction with B(C6F5)3 is about 5 times preferred over H-bonding to (C6F5)3BOH2. The X-ray single-crystal analysis of [2-methyl-3H-indolium]3 provided the first experimental observation of an asymmetric H-bond in the [H3O2]- moiety, the measured O-H and H...O bond distances being significantly different [1.14(2) vs 1.26(2) A]. The reaction of NEt3 with an equimolar mixture of B(C6F5)3 and bis(pentafluorophenyl)borinic acid, (C6F5)2BOH, afforded the novel borinatoborate salt [NHEt3]+ [(C6F5)3BOB(C6F5)2]- ([NHEt3]4). X-ray diffraction showed that the B-O bond distances are significantly shorter than in [(C6F5)3B(mu-OH)B(C6F5)3]-. Variable-temperature 19F NMR revealed high mobility of the five aryl rings, at variance with the more crowded anion 2. 2D NMR correlation experiments showed that in CD2Cl2 the two anions [(C6F5)3BOH]- and [(C6F5)3BH]- form tight ion pairs with [NHEt3]+, in which the NH proton establishes a conventional (BO...HN) or an unconventional (BH...HN), respectively, hydrogen bond with the anion. The diborate anions 2-4, on the contrary, gave loose ion pairs with the ammonium cation, due both to the delocalized anionic charge and to the more sterically encumbered position of the oxygen atoms that should act as H-bond acceptors.     

Intra- and intermolecular N-H...F-C hydrogen-bonding interactions in amine adducts of tris(pentafluorophenyl)borane and -alane

The reaction between B(C(6)F(5))(3) and NH(3)(g) in light petroleum yielded the solvated adduct H(3)N.B(C(6)F(5))(3).NH(3). Treatment with a second equivalent of B(C(6)F(5))(3) afforded H(3)N.B(C(6)F(5))(3). Attempts to prepare the analogous alane adduct were unsuccessful and resulted in protolysis. Related compounds of the form R'R' 'N(H).M(C(6)F(5))(3) were synthesized from M(C(6)F(5))(3) and the corresponding primary and secondary amines (M = B, Al; R' = H, Me, CH(2)Ph; R' ' = Me, CH(2)Ph, CH(Me)(Ph); R'R' ' = cyclo-C(5)H(10)). The solid-state structures of 13 new compounds have been elucidated by single-crystal X-ray diffraction and are discussed. Each of the borane adducts has a significant bifurcated intramolecular hydrogen bond between an amino hydrogen and two o-fluorines, while N-H...F-C interactions in the alane adducts are weaker and more variable. (19)F NMR studies demonstrate that the borane adducts retain the bifurcated C-F...H...F-C hydrogen bond in solution. Compounds of the type R'R' 'N(H).M(C(6)F(5))(3) conform to Etter's rules for the prediction of hydrogen-bonding interactions.     

Synthesis and structures of tris(pentafluorophenyl)silylamines

Tris(pentafluorophenyl)silylamines were synthesized by silylation of amines and imines with (C₆F₅)₃SiCl or (C₆F₅)₃SiOTf in the presence of triethylamine. The crystal structures of the (C₆F₅)₃SiN(H)CH₂Ph and (C₆F₅)₃SiN(CH=CMe₂)CH₂Ph compounds were studied by X-ray diffraction. The crystal packings were analyzed by quantum chemical calculations in terms of the density functional theory (PBE exchange-correlation functional). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1345–1352, July, 2007.     

Triarylamines with branched multi-pyridine groups: modulation of emission properties by structural variation,solvents, and tris(pentafluorophenyl)borane

Six triarylamine derivatives 1–6 with branched multi-pyridine substituents were prepared and characterized. These compounds are distinguished by the substituent on one of the phenyl group with NO2 for 1, CN for 2, Cl for 3, p-C6 H4 OMe for 4, OMe for 5,and NMe2 for 6, respectively. As revealed by single crystal X-ray analysis, these substituents play an important role in determining the configuration of the triarylamine framework and the crystal packing of 1–6. The emission properties of these compounds were examined in different solvents(toluene, CH2 Cl2, acetone, tetrahydrofuran(THF), and N,N-dimethylformamide(DMF)) and in solid states. Distinct dual emissions from the localized emissive state and the intramolecular charge transfer state were observed for compound 5 in CH2 Cl2. Compounds 1 and 6 show apparent aggregated enhanced emissions in acetone/H2 O.The emission properties of these compounds were further modulated by the addition of tris(pentafluorophenyl)borane. In addition, density functional theory(DFT) and time-dependent DFT(TDDFT) calculations have been performed on the ground and singlet excited states to complement the experimental findings.     

Reactivity of thallium tris[tris(pentafluorophenyl)germyl] mercurate

Metallic lithium and dibenzenechromium displace thallium from (R^f₃Ge)₃HgTl·1.5DME (R^f = C₆F₅, DME = 1,2-dimethoxyethane) to give (R^f₃Ge)₃HgLi·3DME and [(R^f₃Ge)₄Hg][Cr(C₆H₆)₂]₂, respectively. Reactions of thallium germylmercurate with halides of metals and organometallics in DME/EtOH solution produce ionic compounds of [(R^f₃Ge)₃Hg]^? M⁺ type, which (depending on “M”) (a) may be isolated as pure compounds, (b) disproportionate, (c) form covalent derivatives R^f₃Ge-m or (d) undergo alcoholysis. A general scheme for the reactions has been proposed.     

Tris(pentafluorophenyl)borane catalyzed Ferrier azaglycosylation with sulfonamides and carbamates

The reaction of tri-O-acetyl-d-glucal with different nitrogen nucleophiles was effectively promoted by a catalytic amount of tris(pentafluorophenyl)borane for the first time in acetonitrile at room temperature to produce a variety of azapseudoglycals via Ferrier rearrangement in good yields and preferential anomeric selectivity.     

Complexation of tris(pentafluorophenyl)silanes with neutral Lewis bases

A detailed analysis of monodentate and bidentate complexation of tris(pentafluorophenyl)silyl (TPFS) derivatives with neutral Lewis bases was performed. The NMR spectroscopy and X-ray diffraction analysis (11 structures) were the key methods to characterize tetra- or pentacoordinate silicon compounds, whereas the peculiarities of crystal packing were analyzed by means of DFT calculations. The interaction of TPFS-X (X = F, Cl, OTf) with strong Lewis bases (HMPA, N-methylpyrrolidinone) may afford three different species: neutral pentacoordinate TPFS(X)-L, cationic tetracoordinate TPFS-L⁺ X⁻, and cationic pentacoordinate TPFS-(L)⁺₂X⁻, representatives of each type were characterized by X-ray diffraction. A variety of complexes with bidentate complexation, featuring the trigonal bipyramidal geometry with apical C₆F₅-group was prepared and structurally characterized. The extent of Si-C_apical bond elongation depends on the donating ability of the coordinating ligand, with the longest Si-C bond of 1.981(1) Å observed for six-membered complex of TPFS-ether of N-(2-hydroxybenzoyl)pyrrolidine.     

Synthesis of tris(cyclopentadienyl)zirconium tetrakis(pentafluorophenyl)borate

Russian Chemical Bulletin - An efficient procedure for the synthesis of tris(cyclopentadienyl)zirconium tetrakis-(pentafluorophenyl)borate [Cp3Zr][B(C6F5)4] was suggested based on the reaction of...     

Calorimetric and structural studies of organic compound of tris(pentafluorophenyl)-4-pyridylethylgermane

In the present research, the temperature dependence of heat capacity of tris(pentafluorophenyl)-4-pyridylethylgermane (C₆F₅)₃Ge–CH₂–CH₂–C₅H₄N was studied by precise adiabatic vacuum calorimetry and differential scanning calorimetry over the temperature range from 6 to 450 K. The temperature and enthalpy of fusion of tris(pentafluorophenyl)-4-pyridylethylgermane and the total mole fraction of impurities have been determined. The thermal stability of the sample was investigated by thermogravimetric analysis. The experimental data were used to calculate the standard thermodynamic functions: heat capacity, enthalpy, entropy, and the Gibbs energy over the range from T → 0 to 420 K for crystalline and liquid states. For the compound under study, the standard entropy of formation in the crystalline state was calculated at T = 298.15 K. In addition, the structure of the investigated compound was established, and corresponding structural parameters were determined.