Trityl Tetrakis Research Articles

Synthesis of low-entangled UHMWiPP using Hf-pyridyl amido catalyst activated by trityl tetrakis (pentafluorophenyl) borate

Recently we demonstrated that low entangled ultra-high molecular weight isotactic polypropylene having molecular weight up to 2.4 million g/mol can be synthesized using a Hf-pyridyl amido catalyst activated by dimethylanilinium tetrakis (pentafluorophenyl)borate. Herein, we used an aprotic borate (trityl tetrakis(pentafluorophenyl)borate) to activate a Hf-pyridyl amido catalyst leading to a fast and ease catalyst activation even at lower temperatures, thus yielding exceptionally high molecular weight (up to 7.7 million g/mol) having improved tacticity (mmmm up to 98.5 %) and peak melting temperature (up to 165 °C). Thus synthesized polymers show extremely slow equilibration process by rheological characterization, indicating the low entangled state. These polymers can be processed in solid-state, without melting, into uniaxial drawn tapes having high tensile strength (1.46 N/tex) and tensile modulus (33 N/tex). The superior mechanical properties enable the tapes to be used as reinforcing material for commercial polypropylene grades, opening the possibilities of making one-component easy-to-recycle composites.

Dopant-induced Morphology of Organic Semiconductors Resulting in High Doping Performance.

Doping plays a crucial role in modulating and enhancing the performance of organic semiconductor (OSC) devices. In this study, the critical role of dopants is underscored in shaping the morphology and structure of OSC films, which in turn profoundly influences their properties. Two dopants, trityl tetrakis(pentafluorophenyl) (TrTPFB) and N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate (DMA-TPFB), are examined for their doping effects on poly(3-hexylthiophene) (P3HT) and PBBT-2T host OSCs. It is found that although TrTPFB exhibits higher doping efficiency, OSCs doped with DMA-TPFB achieve comparable or even enhanced electrical conductivity. Indeed, the electrical conductivity of DMA-TPFB-doped P3HT reaches over 67 S cm-1, which is a record-high value for mixed-solution-doped P3HT. This can be attributed to DMA-TPFB inducing a higher degree of crystallinity and reduced structural disorder. Moreover, the beneficial impact of DMA-TPFB on the OSC films' morphology and structure results in superior thermoelectric performance in the doped OSCs. These findings highlight the significance of dopant-induced morphological and structural considerations in enhancing the film characteristics of OSCs, opening up a new avenue for optimization of dopant performance.

Group transfer polymerization in bulk methacrylates

AbstractGroup transfer polymerization (GTP) is a polymerization method developed to obtain targeted (meth)acrylic polymers in solution at ambient temperatures. In this work, it is employed with methacrylic monomers to obtain low Ð polymers in bulk. In this regard, different initiator systems that exhibit different mechanisms are compared concerning the molecular weight, the polydispersity and double bond conversion of the resulting bulk polymers. The respective systems were chosen carefully to give a broad overview of earlier developed initiator‐catalyst combinations 1‐methoxy‐1‐(trimethylsiloxy)‐2‐methylprop‐1‐ene (MTS) & tetrabutylammonium cyanide (TBACN) and more recently investigated initiating systems MTS & trityl tetrakis(pentafluorophenyl)borate (TTPB) or dimethyl phenyl silane (DMPS) & tris(pentafluorophenyl)borate (BCF). The described initiating systems are applied as a two‐component (2K) system to ensure a homogeneous distribution of the respective initiator and catalyst in the bulk monomer. In addition to the 2K experiments, photochemical initiation is also applied to bulk formulations. Therefore, a photoacid generator (PAG) and MTS is used to trigger the polymerization reaction by irradiation with UV light. A highly controlled photopolymerization method in bulk was developed that way achieving a low polydispersity polymer with high double bond conversion.

Revealing the Electrophilic-Attack Doping Mechanism for Efficient and Universal p-Doping of Organic Semiconductors.

Doping is of great importance to tailor the electrical properties of semiconductors. However, the present doping methodologies for organic semiconductors (OSCs) are either inefficient or can only apply to some OSCs conditionally, seriously limiting their general applications. Herein, a novel p-doping mechanism is revealed by investigating the interactions between the dopant trityl tetrakis(pentafluorophenyl) borate (TrTPFB) and poly(3-hexylthiophene) (P3HT). It is found that electrophilic attack of the trityl cations on thiophenes results in the formation of tritylated thiophenium ions, which subsequently induce electron transfer from neighboring P3HT chains to realize p-doping. This unique p-doping mechanism enables TrTPFB to p-dope various OSCs including those with high ionization energy (IE≈5.8eV). Moreover, this doping mechanism endows TrTPFB with strong doping capability, leading to doping efficiency of over 80% in P3HT. The discovery and elucidation of this novel doping mechanism not only points out that strong electrophiles are a class of efficient p-dopants for OSCs, but also provides new opportunities toward highly efficient doping of various OSCs.

Improvement of catalytic activity for α‐diimine nickel complex with active sites stabilized by bulky boron counterions at elevated temperature

Three α‐diimine Ni (II) catalysts (Cat.1, Cat.2 and Cat.3) were synthesized and investigated for ethylene polymerization using alkyl aluminum and organoboron compounds as binary cocatalyst. The effects of different alkyl aluminum and boron complexes on ethylene polymerization catalyzed by Cat.1, Cat.2, and Cat.3 were studied. The sodium tetrakis[3,5‐bis (trifluoromethyl)phenyl]borate (NaBArF) was found to have best promotion for the catalytic activity of Cat.1, compared to negative effect of dimethylanilinium tetrakis (pentafluorophenyl)borate (TTB) and trityl tetrakis (pentafluorophenyl)borate (AB). All the three catalysts showed higher catalytic activity when NaBArF was introduced into the catalytic system, especially for Cat.3 (increased by 41.3% at 70°C). There was still minor increase of the catalytic activity for Cat.2 which have much better thermostability than Cat.3. The charging sequence of NaBArF and the [B]/[Ni] ratio have significant effects on the catalytic activity. The better catalytic performance of Cat.1/AlEt2Cl/NaBArF could be explained by its ability to raise the number of active centers. Namely, the molar percentage of active centers of Cat.1/AlEt2Cl/NaBArF was still above 30%, which was 1.7 times that of Cat.1/AlEt2Cl even if polymerization ran up to 30 min based on 2‐thiophenecarbonyl chloride (TPCC) quench‐labeling method. Lower [Al]/[Ni] ratio but more active centers and longer active centers lifetime of this binary cocatalyst is promising for improving the activity of ethylene polymerization industrially at elevated temperature.

Doping Polymer Semiconductors by Organic Salts: Toward High-Performance Solution-Processed Organic Field-Effect Transistors.

Solution-processed organic field-effect transistors (OFETs) were fabricated with the addition of an organic salt, trityl tetrakis(pentafluorophenyl)borate (TrTPFB), into thin films of donor-acceptor copolymer semiconductors. The performance of OFETs is significantly enhanced after the organic salt is incorporated. TrTPFB is confirmed to p-dope the organic semiconductors used in this study, and the doping efficiency as well as doping physics was investigated. In addition, systematic electrical and structural characterizations reveal how the doping enhances the performance of OFETs. Furthermore, it is shown that this organic salt doping method is feasible for both p- and n-doping by using different organic salts and, thus, can be utilized to achieve high-performance OFETs and organic complementary circuits.

New reactivity at the silicon bridge in sila[1]ferrocenophanes.

We describe two new types of reactivity involving silicon-bridged [1]ferrocenophanes. In an attempt to form a [1]ferrocenophane with a bridging silyl cation, the reaction of sila[1]ferrocenophane [Fe(η-C5H4)2Si(H)TMP] (12) (TMP = 2,2,6,6-tetramethylpiperidyl) towards the hydride-abstraction reagent trityl tetrakis(pentafluorophenyl)borate ([CPh3][B(C6F5)4]) was explored. This yielded the unusual dinuclear species [Fe(η-C5H4)2Si(TMP·H)(η-C5H3)Fe(η-C5H4)Si(H)TMP][B(C6F5)4] [13][B(C6F5)4] in low yield. The formation of [13]+ is proposed to involve abstraction of hydride from the silicon bridge in 12 with subsequent C-H bond cleavage of a cyclopentadienyl group by the resulting electrophilic transient silyl cation intermediate. We also explored the reaction of dimethylsila[1]ferrocenophane [Fe(η-C5H4)2SiMe2] (1) with the Au(i) species AuCl(PMe3). This was found to result in addition of the Au-Cl bond across the Cpipso-Si bond to yield the ring-opened species [1'-(chlorodimethylsilyl)-ferrocenyl](trimethylphosphine)gold(i), [Fe(C5H4SiMe2Cl){C5H4Au(PMe3)}] (14). This represents the first example of ring-opening addition of a metallocenophane with a reagent possessing a transition metal-halogen bond.

Synthesis of π-Extended Siloles Using Intramolecular Chain Hydrosilylation

Intramolecular chain hydrosilylation afforded benzo- and naphtho-fused siloles in 20–81% yields from the corresponding hydrosilanes in the presence of a small amount of trityl tetrakis(pentafluorophenyl)borate as an initiator. This hydrosilylation can be applied for the synthesis of disiloles such as 1,5-disila-1,5-dihydro-s-indacene and naphthodisiloles.

Frustrated Lewis Pair vs Metal–Carbon σ-Bond Insertion Chemistry at an o-Phenylene-Bridged Cp2Zr+/PPh2 System

Methyl anion abstraction from (o-diphenylphosphino)phenyl(methyl)zirconocene by trityl tetrakis(pentafluorophenyl)borate gives the o-phenylene-bridged Zr+/P system 10. It behaves toward a variety of reagents as a typical Zr+/P frustrated Lewis pair (FLP). It undergoes cooperative 1,4-addition reactions to some chalcone derivatives and adds in a 1,2-fashion to a variety of organic carbonyls and to several heterocumulenes. The reactive Zr–C σ bond of the FLP 10 remains intact in these reactions. Complex 10 splits dihydrogen, but subsequently the Zr–C σ bond is protonolytically cleaved in this case. Only a few special reagents, among them carbon monoxide, undergo the usual insertion reaction into the Zr–C(aryl) σ-bond of the Zr+/P system 10.

ChemInform Abstract: Regioselective and Stereospecific Dehydrogenative Annulation Utilizing Silylium Ion‐Activated Alkenes.

Treatment of dialkylbenzylsilanes (1) with trityl tetrakis(pentafluorophenyl)borate (TPFPB) afforded the corresponding silylium ions in equilibrium with their intra- or intermolecular π-complexes, which underwent dehydrogenative annulation with various alkenes to form 1,2,3,4-tetrahydro-2-silanaphthalenes (4) in up to 82% isolated yield. Sterically bulkier substituents on the silicon atom tended to increase the yield of cyclic products 4. The annulation products retained the stereochemistry in cases of the reactions using internal alkenes. The use of diisopropyl(1-naphthyl)silane (2) instead of 1 also resulted in annulation to obtain the 2,3-dihydro-1-sila-1H-phenalene derivatives 6. Electrophilic aromatic substitution at the 8-position was predominant, despite the two potentially reactive positions on the naphthyl group. The steric hindrance of the naphthyl group prevented addition of the cis-alkene to the silylium ion, which would considerably decrease yields of the desired products from 2 compared to t...

Intramolecular Chain Hydrosilylation of Alkynylphenylsilanes Using a Silyl Cation as a Chain Carrier.

Diorganyl[2-(trimethylsilylethynyl)phenyl]silanes 1a–c and methyl-substituted phenylsilanes 1d and 1e were treated with a small amount of trityl tetrakis(pentafluorophenyl)borate (TPFPB) as an initiator in benzene to afford the corresponding benzosiloles (2a–e) in moderate to good yields. However, no reaction was observed for the reaction using [2-(1-hexynyl)phenyl]diisopropylsilane lf. The methyl substituent was tolerated under the reaction conditions and increased the yield of the corresponding benzosilole depending on the substitution position. From the result using 1f, the current reaction was found to require the trimethylsilyl group, which can stabilize intermediary alkenyl carbocations by the β-silyl effect. The current reaction can be considered an intramolecular chain hydrosilylation of alkynylarylsilanes involving silyl cations as chain carriers. Therefore, the silyl cations generated by hydride abstraction from hydrosilanes 1 with the trityl cation causes intramolecular electrophilic addition to the C-C triple bond to form ethenyl cations, which abstract a hydride from 1 to afford benzosiloles 2 with the regeneration of the silyl cations.

Regioselective and Stereospecific Dehydrogenative Annulation Utilizing Silylium Ion-Activated Alkenes.

Treatment of dialkylbenzylsilanes (1) with trityl tetrakis(pentafluorophenyl)borate (TPFPB) afforded the corresponding silylium ions in equilibrium with their intra- or intermolecular π-complexes, which underwent dehydrogenative annulation with various alkenes to form 1,2,3,4-tetrahydro-2-silanaphthalenes (4) in up to 82% isolated yield. Sterically bulkier substituents on the silicon atom tended to increase the yield of cyclic products 4. The annulation products retained the stereochemistry in cases of the reactions using internal alkenes. The use of diisopropyl(1-naphthyl)silane (2) instead of 1 also resulted in annulation to obtain the 2,3-dihydro-1-sila-1H-phenalene derivatives 6. Electrophilic aromatic substitution at the 8-position was predominant, despite the two potentially reactive positions on the naphthyl group. The steric hindrance of the naphthyl group prevented addition of the cis-alkene to the silylium ion, which would considerably decrease yields of the desired products from 2 compared to those from 1.

The Cyclohexadienyl-Leaving-Group Approach toward Donor-Stabilized Silylium Ions

The cyclohexa-2,5-dien-1-yl group is established as a leaving group at silicon as an alternative to the Bartlett–Condon–Schneider silicon-to-carbon hydride transfer and the allyl-leaving-group approach to generate silylium ions. Hydride abstraction from the skipped diene unit employing trityl tetrakis(pentafluorophenyl)borate (1, [Ph3C]+[B(C6F5)4]−) yields the silicon cation along with benzene. Our investigations reveal that the presence of an internal or external donor group is mandatory to allow for the formation of intra- or intermolecularly stabilized silylium ions. If not, degradation of the precursor is observed as a result of the reaction of the allylic silane units with the released silylium ion. It is also shown that such allylic silanes do form remarkably stable alkyl-substituted carbenium ions when reacted stoichiometrically with benzene-stabilized silylium ions.

도입된 High α-olefin의 사슬길이 변화에 따른 삼원공중합체 특성 변화

본 연구에서는 여러가지 메탈로센 촉매 및 trityl tetrakis(pentafluorophenyl)borate/triisobutylaluminium 공촉매 시스템을 이용하여 에틸렌, high <TEX>${\alpha}$</TEX>-olefin 및 divinylbenzene으로 구성된 삼원공중합체를 중합하였다. 우선 삼원공중합체 중합에 있어서, 최적의 촉매를 확보하기 위해 rac-<TEX>$Et(Ind)_2ZrCl_2$</TEX>, rac-<TEX>$SiMe_2(Ind)_2ZrCl_2$</TEX>, rac-<TEX>$SiMe_2(2-Me-Ind)_2ZrCl_2$</TEX> 등의 메탈로센 촉매들과 trityl tetrakis(pentafluorophenyl)borate/triisobutylaluminium 공촉매 시스템을 이용하여 삼원공중합체의 촉매활성도, 분자량 및 분자량 분포도를 비교하였다. 공단량체로 투입되는 high <TEX>${\alpha}$</TEX>-olefin의 사슬 길이 변화가 삼원공중합에 미치는 영향을 살펴보기 위해 여러 가지 중합 조건들은 동일하게 유지하면서 1-hexene, 1-octene, 1-decene 또는 1-dodecene을 도입한 삼원공중합체들을 각각 합성하였다. 이와 같이 준비한 삼원공중합체들의 화학 조성, 열적 특성 및 기계적 물성 등을 비교 분석하였다. In this study, we prepared poly(ethylene-ter-1-hexene-ter-divinylbenzene) using various metallocene catalysts with trityl tetrakis(pentafluorophenyl)borate/triisobutylaluminium cocatalysts system. We tried rac-<TEX>$Et(Ind)_2ZrCl_2$</TEX>, rac-<TEX>$SiMe_2(Ind)_2ZrCl_2$</TEX>, and rac-<TEX>$SiMe_2(2-Me-Ind)_2ZrCl_2$</TEX> to choose optimum metallocene catalyst, comparing with catalytic activity, molecular weight, molecular weight distribution of the terpolymers. To study the effects of chain length of high <TEX>${\alpha}$</TEX>-olefins on the terpolymerization, we synthesized the terpolymers using 1-hexene, 1-octene, 1-decene or 1-dodecene. We characterized chemical composition, thermal properties, and mechanical properties of the terpolymers.

Cationic Alkylaluminum-Complexed Zirconocene Hydrides: NMR-Spectroscopic Identification, Crystallographic Structure Determination, and Interconversion with Other Zirconocene Cations

The ansa-zirconocene complex rac-Me(2)Si(1-indenyl)(2)ZrCl(2) ((SBI)ZrCl(2)) reacts with diisobutylaluminum hydride and trityl tetrakis(perfluorophenyl)borate in hydrocarbon solutions to give the cation [(SBI)Zr(μ-H)(3)(Al(i)Bu(2))(2)](+), the identity of which is derived from NMR data and supported by a crystallographic structure determination. Analogous reactions proceed with many other zirconocene dichloride complexes. [(SBI)Zr(μ-H)(3)(Al(i)Bu(2))(2)](+) reacts reversibly with ClAl(i)Bu(2) to give the dichloro-bridged cation [(SBI)Zr(μ-Cl)(2)Al(i)Bu(2)](+). Reaction with AlMe(3) first leads to mixed-alkyl species [(SBI)Zr(μ-H)(3)(AlMe(x)(i)Bu(2-x))(2)](+) by exchange of alkyl groups between aluminum centers. At higher AlMe(3)/Zr ratios, [(SBI)Zr(μ-Me)(2)AlMe(2)](+), a constituent of methylalumoxane-activated catalyst systems, is formed in an equilibrium, in which the hydride cation [(SBI)Zr(μ-H)(3)(AlR(2))(2)](+) strongly predominates at comparable HAl(i)Bu(2) and AlMe(3) concentrations, thus implicating the presence of this hydride cation in olefin polymerization catalyst systems.

ChemInform Abstract: The Trityl Tetrakis(pentafluorophenyl)borate Catalyzed Stereoselective Glycosylation Using New Glycosyldonor, 3,4,6-Tri-O-benzyl-2-O-p-toluoyl-β-D-glucopyranosyl Phenylcarbonate.

The trityl tetrakis(pentafluorophenyl)borate [TrB(C6F5)4] catalyzed stereoselective synthesis of various disaccharides was successfully carried out by treating a new 2-O-acyl-protected glycosyl donor, 3,4,6-tri-O-benzyl-2-O-p-toluoyl-β-D-glucopyranosyl phenylcarbonate, with several glycosyl acceptors, thioglycosides, affording the corresponding disaccharides in high yields.

ChemInform Abstract: Stereoselective Glycosylation of Thioglycosides Promoted by Respective Combinations of N-Iodo- or N-Bromosuccinimide and Trityl Tetrakis(pentafluorophenyl)borate. Application to One-Pot Sequential Synthesis of Trisaccharide.

New highly effective promoter system for the glycosylation of thioglycoside, the combined use of stoichiometric amount of either N-iodosuccinimide or N-bromosuccinimide and a catalytic amount of TrB(C6F5)4, was developed and was successfully applied to the one-pot sequential synthesis of trisaccharides. In the first glycosylation step, 3,4,6-tri-O-benzyl-2-O-p-toluoyl-β-D-glucopyranosyl phenylcarbonate was treated with thioglycosides in the presence of a catalytic amount of TrB(C6F5)4 alone, and the following glycosylation with methyl α-D-glycosides was carried out by further addition of either N-iodosuccinimide or N-bromosuccinimide to the initially resulted reaction mixture to afford the corresponding trisaccharides in one-pot manner.

Gas Phase Polymerization of Ethylene with Supported α-Diimine Nickel(II) Catalysts

An efficient synthetic strategy for new 2,5- and 2,6-substituted unbridged and 1,4-dithiane bridged ligands is presented. The reaction of the latter compounds with Ni(acac)2 and trityl tetrakis(pentafluorophenyl)borate gave the corresponding Ni(II) complexes in high yields. The structure of one of these complexes was determined by X-ray analysis. These complexes were supported on silica without a chemical tether and were used as catalysts for ethylene polymerization reactions in the gas phase. Furthermore, ethylene was polymerized with the unsupported 2,5-complexes in homogeneous solution for comparison. The influence of the ligand structure, hydrogen and temperature on the polymerization performance was investigated. The supported catalysts showed moderate to high activities and produced polyethylenes ranging from HDPE to LLDPE, without further addition of an 1-olefin comonomer. In contrast to 2,6-complexes, which generate high molecular weight polyethylene, the 2,5-compounds afford materials of lower molecular weight comprising terminal and internal double bonds. In addition, video microscopy experiments allowed to investigate the growth of single polyethylene particles. Electron microscopy was applied to show that their morphology is a replicate of the starting catalyst grains.

Influence of cocatalyst on the stereoselectivity and productivity of styrene polymerization reactions

Influence of different cocatalysts on the polymerization reaction of styrene using heterogeneous nanoparticle NA-MgO and NA-TiO2 (anatase) supported bis (cyclopentadienyl) zirconium dichloride catalysts is studied. Methyaluminoxane, trityl tetrakis(pentafluorophenyl)borate(1), dimethylanilinium tetrakis (pentafluoro-phenyl)borate (2) and tris(pentafluorophenyl)borane (3) are used as cocatalysts for this study. The productivity and stereoselectivity of the catalysts systems are found to be highest with MAO and lowest with the borane 3 (MAO > 1> 2 > 3). Catalysts derived from the borane 3 yield amorphous atactic polystyrenes but those from cocatalysts MAO, 1, or 2 yield crystalline, syndiotactic polystyrenes under the same reaction conditions. Effects of addition of various scavengers and solvents with different polarities on styrene polymerizations are also reported here. Characterization of the obtained polymers is done by Gel Permeation Chromatography, 13C-NMR spectroscopy and Differential Scanning Calorimetry.

C3-Symmetric Chiral Organolanthanide Complexes: Synthesis, Characterization, and Stereospecific Polymerization of α-Olefins

The trialkyl complexes [M(iPr-trisox)(CH2SiMe2R)3] (R = Me, M = Y, (1), R = Ph, M = Lu (2a), R = Me, M = Lu (2b), Tm (3), Er (4), Ho (5), and Dy (6)) were prepared from 1,1,1-tris[(S)-4-isopropyloxazolinyl]ethane (iPr-trisox) and the corresponding trialkyl precursors [M(CH2SiMe2R)3(THF)n]. Their molecular structures all display a highly distorted octahedral geometry, with the angles subtended at the metal center significantly deviating from the ideal 90°, which is attributed to the steric demands imposed by the large CH2SiMe2R ligands, both with each other and with the isopropyl groups of the iPr-trisox ligand. Active catalysts for the polymerization of α-alkenes (n-hexene, n-heptene, and n-octene) were generated in situ by reaction of the trialkyl precatalyst with 2 equiv of trityl tetrakis(pentafluorophenyl)borate. In all cases polyolefins with Mw/Mn values of between 1.58 and 2.08 and isotacticities of 80−95% were obtained. The polymerization activity increases from lutetium to thulium and then subsequently decreases with increasing ionic radius of the metal due to a combination of activation with increasing ionic radius and decreasing catalyst stability.