Synthesis and Characterization of Phosphinobenzenamine Palladium Complexes and Their Application in Ethylene Polymerization and Copolymerization with Polar Monomers

A series of phosphinobenzenamine palladium complexes Pd1–Pd5 with different substituents was successfully synthesized and characterized. X-ray diffraction analysis of Pd1, Pd2, and Pd4 revealed that the palladium complexes exhibited an almost square–planar geometry and structural distinctions compared with previously reported N∧P-based palladium complexes. These palladium complexes exhibited high activity (4.92 × 105 g mol–1 h–1) toward ethylene polymerization with excellent thermal stability up to 100 °C to produce semicrystalline polyethylenes bearing unsaturated vinylene/vinyl groups with moderate branch densities (15–26/1000 C). Most importantly, they could promote the copolymerization of ethylene and polar monomers, such as methyl acrylate (MA) and 5-hexene-1-yl-acetate (HAc), even at a high temperature of 80 °C

Highly Active <i>ansa</i>-(Fluorenyl)(amido)titanium-Based Catalysts with Low Load of Methylaluminoxane for Syndiotactic-Specific Living Polymerization of Propylene

<i>ansa</i>-Dimethylsilylene­(fluorenyl)­(amido)titanium complexes bearing various electron-donating substituents are synthesized and applied to propylene polymerization by the use of MMAO/2,6-di-<i>tert</i>-butyl-4-methylphenol as a cocatalyst. The complexes containing adamantylamido ligands (<b>1a</b>,<b>b</b>) show unexpectedly high activity (31150 kg of polymer (mol of Ti)⁻¹ h^–1) with a low Al:Ti ratio of 20. The catalysts also promote syndiotactic-specific living polymerization to produce propylene-ethylene block copolymers

Enhancement of Chain Growth and Chain Transfer Rates in Ethylene Polymerization by (Phosphine-sulfonate)PdMe Catalysts by Binding of B(C₆F₅)₃ to the Sulfonate Group

Binding of B­(C₆F₅)₃ to a sulfonate oxygen of (<i>ortho</i>-phosphino-arenesulfonate)­PdR catalysts results in a 3–4 fold increase in the rate of chain growth and a larger increase in the rate of chain transfer. The reaction of (PO-Et)­PdMe­(py) (<b>1a</b>, [PO-Et]⁻ = <i>ortho</i>-{(2-Et-Ph)₂P}-<i>para</i>-toluenesulfonate) with 1 equiv of B­(C₆F₅)₃ yields the base-free dimer {(PO-Et)­PdMe}₂ (<b>2a</b>), in which the (PO-Et)­PdMe units are linked through an eight-membered [PdSO₂]₂ ring. The reaction of {(PO-3,5-^<i>t</i>Bu₂)­PdMe}₂(TMEDA) (<b>4b</b>; [PO-3,5-^<i>t</i>Bu₂]⁻ = <i>ortho</i>-{(3,5-^<i>t</i>Bu₂-Ph)₂P}-<i>para</i>-toluenesulfonate, TMEDA = <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetramethylethylenediamine) with BF₃·Et₂O yields the soluble base-free dimer {(PO-3,5-^<i>t</i>Bu₂)­PdMe}₂ (<b>2b</b>), in which the (PO-3,5-^<i>t</i>Bu₂)­PdMe units are linked through a four-membered Pd₂O₂ ring. <b>2b</b> reacts with 2 equiv of B­(C₆F₅)₃ to yield {[PO·B­(C₆F₅)₃-3,5-^<i>t</i>Bu₂]­PdMe}₂ (<b>5b</b>, [PO·B­(C₆F₅)₃-3,5-^<i>t</i>Bu₂]⁻ = [2-{(3,5-^<i>t</i>Bu₂-Ph)₂P}-4-Me-C₆H₃SO₂OB­(C₆F₅)₃]⁻), which crystallizes from Et₂O as the monomeric complex [PO·B­(C₆F₅)₃-3,5-^<i>t</i>Bu₂]­PdMe­(Et₂O) (<b>6b</b>). In both <b>5b</b> and <b>6b</b>, the B­(C₆F₅)₃ binds to a sulfonate oxygen. In toluene solution at 60 °C, <b>2b</b> polymerizes ethylene (80 psi) to linear polyethylene with <i>M</i>_n = 3,000, while the B­(C₆F₅)₃ adducts <b>5b</b> and <b>6b</b> yield ethylene oligomers (<i>M</i>_n = 160–170). <b>5b</b> and <b>6b</b> are 3–4 times more active than <b>2b</b>. Similarly, <b>1a</b> polymerizes ethylene to linear polyethylene with <i>M</i>_n = 29,300 (toluene, 80 °C, 435 psi), while <b>1a</b>-4 B­(C₆F₅)₃ yields polymer with <i>M</i>_n = 2,520 with a 4 fold increase in activity. <b>2b</b> reacts with ethylene at 7 °C to form the ethylene adduct (PO-3,5-^<i>t</i>Bu₂)­PdMe­(CH₂CH₂) (<b>7b</b>) followed by multiple insertions to generate (PO-3,5-^<i>t</i>Bu₂)­Pd­(CH₂CH₂)_<i>n</i>CH₃ species. In contrast, <b>5b</b> reacts with ethylene to form [PO·B­(C₆F₅)₃-3,5-^<i>t</i>Bu₂]­PdMe­(CH₂CH₂) (<b>8b</b>) followed by insertion and β-H transfer to yield propene with subsequent catalytic formation of 1-butene and higher olefins. The rate of ethylene insertion of <b>8b</b> is 3 times greater than that of <b>7b</b>, consistent with the batch polymerization results. The polymer yield and molecular weight data show that binding of B­(C₆F₅)₃ to <b>2b</b> and <b>1a</b> increases the chain transfer rates by a factor of 80 and 42, respectively

Enhancement of Chain Growth and Chain Transfer Rates in Ethylene Polymerization by (Phosphine-sulfonate)PdMe Catalysts by Binding of B(C₆F₅)₃ to the Sulfonate Group

Binding of B­(C₆F₅)₃ to a sulfonate oxygen of (<i>ortho</i>-phosphino-arenesulfonate)­PdR catalysts results in a 3–4 fold increase in the rate of chain growth and a larger increase in the rate of chain transfer. The reaction of (PO-Et)­PdMe­(py) (<b>1a</b>, [PO-Et]⁻ = <i>ortho</i>-{(2-Et-Ph)₂P}-<i>para</i>-toluenesulfonate) with 1 equiv of B­(C₆F₅)₃ yields the base-free dimer {(PO-Et)­PdMe}₂ (<b>2a</b>), in which the (PO-Et)­PdMe units are linked through an eight-membered [PdSO₂]₂ ring. The reaction of {(PO-3,5-^<i>t</i>Bu₂)­PdMe}₂(TMEDA) (<b>4b</b>; [PO-3,5-^<i>t</i>Bu₂]⁻ = <i>ortho</i>-{(3,5-^<i>t</i>Bu₂-Ph)₂P}-<i>para</i>-toluenesulfonate, TMEDA = <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetramethylethylenediamine) with BF₃·Et₂O yields the soluble base-free dimer {(PO-3,5-^<i>t</i>Bu₂)­PdMe}₂ (<b>2b</b>), in which the (PO-3,5-^<i>t</i>Bu₂)­PdMe units are linked through a four-membered Pd₂O₂ ring. <b>2b</b> reacts with 2 equiv of B­(C₆F₅)₃ to yield {[PO·B­(C₆F₅)₃-3,5-^<i>t</i>Bu₂]­PdMe}₂ (<b>5b</b>, [PO·B­(C₆F₅)₃-3,5-^<i>t</i>Bu₂]⁻ = [2-{(3,5-^<i>t</i>Bu₂-Ph)₂P}-4-Me-C₆H₃SO₂OB­(C₆F₅)₃]⁻), which crystallizes from Et₂O as the monomeric complex [PO·B­(C₆F₅)₃-3,5-^<i>t</i>Bu₂]­PdMe­(Et₂O) (<b>6b</b>). In both <b>5b</b> and <b>6b</b>, the B­(C₆F₅)₃ binds to a sulfonate oxygen. In toluene solution at 60 °C, <b>2b</b> polymerizes ethylene (80 psi) to linear polyethylene with <i>M</i>_n = 3,000, while the B­(C₆F₅)₃ adducts <b>5b</b> and <b>6b</b> yield ethylene oligomers (<i>M</i>_n = 160–170). <b>5b</b> and <b>6b</b> are 3–4 times more active than <b>2b</b>. Similarly, <b>1a</b> polymerizes ethylene to linear polyethylene with <i>M</i>_n = 29,300 (toluene, 80 °C, 435 psi), while <b>1a</b>-4 B­(C₆F₅)₃ yields polymer with <i>M</i>_n = 2,520 with a 4 fold increase in activity. <b>2b</b> reacts with ethylene at 7 °C to form the ethylene adduct (PO-3,5-^<i>t</i>Bu₂)­PdMe­(CH₂CH₂) (<b>7b</b>) followed by multiple insertions to generate (PO-3,5-^<i>t</i>Bu₂)­Pd­(CH₂CH₂)_<i>n</i>CH₃ species. In contrast, <b>5b</b> reacts with ethylene to form [PO·B­(C₆F₅)₃-3,5-^<i>t</i>Bu₂]­PdMe­(CH₂CH₂) (<b>8b</b>) followed by insertion and β-H transfer to yield propene with subsequent catalytic formation of 1-butene and higher olefins. The rate of ethylene insertion of <b>8b</b> is 3 times greater than that of <b>7b</b>, consistent with the batch polymerization results. The polymer yield and molecular weight data show that binding of B­(C₆F₅)₃ to <b>2b</b> and <b>1a</b> increases the chain transfer rates by a factor of 80 and 42, respectively

Enhancement of Chain Growth and Chain Transfer Rates in Ethylene Polymerization by (Phosphine-sulfonate)PdMe Catalysts by Binding of B(C₆F₅)₃ to the Sulfonate Group

Binding of B­(C₆F₅)₃ to a sulfonate oxygen of (<i>ortho</i>-phosphino-arenesulfonate)­PdR catalysts results in a 3–4 fold increase in the rate of chain growth and a larger increase in the rate of chain transfer. The reaction of (PO-Et)­PdMe­(py) (<b>1a</b>, [PO-Et]⁻ = <i>ortho</i>-{(2-Et-Ph)₂P}-<i>para</i>-toluenesulfonate) with 1 equiv of B­(C₆F₅)₃ yields the base-free dimer {(PO-Et)­PdMe}₂ (<b>2a</b>), in which the (PO-Et)­PdMe units are linked through an eight-membered [PdSO₂]₂ ring. The reaction of {(PO-3,5-^<i>t</i>Bu₂)­PdMe}₂(TMEDA) (<b>4b</b>; [PO-3,5-^<i>t</i>Bu₂]⁻ = <i>ortho</i>-{(3,5-^<i>t</i>Bu₂-Ph)₂P}-<i>para</i>-toluenesulfonate, TMEDA = <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetramethylethylenediamine) with BF₃·Et₂O yields the soluble base-free dimer {(PO-3,5-^<i>t</i>Bu₂)­PdMe}₂ (<b>2b</b>), in which the (PO-3,5-^<i>t</i>Bu₂)­PdMe units are linked through a four-membered Pd₂O₂ ring. <b>2b</b> reacts with 2 equiv of B­(C₆F₅)₃ to yield {[PO·B­(C₆F₅)₃-3,5-^<i>t</i>Bu₂]­PdMe}₂ (<b>5b</b>, [PO·B­(C₆F₅)₃-3,5-^<i>t</i>Bu₂]⁻ = [2-{(3,5-^<i>t</i>Bu₂-Ph)₂P}-4-Me-C₆H₃SO₂OB­(C₆F₅)₃]⁻), which crystallizes from Et₂O as the monomeric complex [PO·B­(C₆F₅)₃-3,5-^<i>t</i>Bu₂]­PdMe­(Et₂O) (<b>6b</b>). In both <b>5b</b> and <b>6b</b>, the B­(C₆F₅)₃ binds to a sulfonate oxygen. In toluene solution at 60 °C, <b>2b</b> polymerizes ethylene (80 psi) to linear polyethylene with <i>M</i>_n = 3,000, while the B­(C₆F₅)₃ adducts <b>5b</b> and <b>6b</b> yield ethylene oligomers (<i>M</i>_n = 160–170). <b>5b</b> and <b>6b</b> are 3–4 times more active than <b>2b</b>. Similarly, <b>1a</b> polymerizes ethylene to linear polyethylene with <i>M</i>_n = 29,300 (toluene, 80 °C, 435 psi), while <b>1a</b>-4 B­(C₆F₅)₃ yields polymer with <i>M</i>_n = 2,520 with a 4 fold increase in activity. <b>2b</b> reacts with ethylene at 7 °C to form the ethylene adduct (PO-3,5-^<i>t</i>Bu₂)­PdMe­(CH₂CH₂) (<b>7b</b>) followed by multiple insertions to generate (PO-3,5-^<i>t</i>Bu₂)­Pd­(CH₂CH₂)_<i>n</i>CH₃ species. In contrast, <b>5b</b> reacts with ethylene to form [PO·B­(C₆F₅)₃-3,5-^<i>t</i>Bu₂]­PdMe­(CH₂CH₂) (<b>8b</b>) followed by insertion and β-H transfer to yield propene with subsequent catalytic formation of 1-butene and higher olefins. The rate of ethylene insertion of <b>8b</b> is 3 times greater than that of <b>7b</b>, consistent with the batch polymerization results. The polymer yield and molecular weight data show that binding of B­(C₆F₅)₃ to <b>2b</b> and <b>1a</b> increases the chain transfer rates by a factor of 80 and 42, respectively

Synthesis, Structures, and Norbornene Polymerization Behavior of Neutral Nickel(II) and Palladium(II) Complexes Bearing Aryloxide Imidazolidin-2-imine Ligands

A series of novel aryloxide imidazolidin-2-imine bidentate neutral Ni­(II) and Pd­(II) complexes bearing five- and six-membered chelate ring structures were synthesized and characterized. X-ray diffraction analysis results revealed that all of the Ni­(II) complexes (<b>Ni1</b>–<b>Ni3</b>) and Pd­(II) complexes (<b>Pd1</b> and <b>Pd3</b>) adopted an almost square-planar geometry. In the presence of various cocatalysts such as MAO, MMAO, Et₂AlCl, and EtAlCl₂, all of the Ni­(II) and Pd­(II) complexes exhibited remarkably high activities (up to 2.6 × 10⁷ g of PNB (mol of M)⁻¹ h^–1) toward the addition polymerization of norbornene. These catalyst systems produced high-molecular-weight polynorbornene (PNB) with narrow molecular weight distribution, except for the insoluble PNB obtained with <b>Pd1</b>–<b>Pd3</b>/MAO systems. The Pd­(II) complexes showed particularly good thermostability with a high activity of 1.56 × 10⁷ g of PNB (mol of Pd)⁻¹ h^–1 even at 80 °C. These complexes are rare examples of neutral Ni­(II) and Pd­(II) complexes bearing aryloxide-functionalized imidazolidin-2-imine ligands in the field of olefin polymerization

Highly Robust Nickel Catalysts Containing Anilinonaphthoquinone Ligand for Copolymerization of Ethylene and Polar Monomers

Copolymerizations of ethylene with polar monomers such as 5-hexene-1-yl acetate and allyl acetate are explored using nickel complexes bearing a class of anilino­naphthoquinone ligands. High tolerability of this complex toward polar comonomer is achieved by the installation of sterically bulky substituent on the aniline ligand. Moreover, the heterogenization of the nickel complexes using silica-supported modified methylaluminoxane enhances the copolymerization performances. The catalyst is highly active and thermally stabile to give semicrystalline ester-functionalized high molecular weight polyethylenes

An Amylase-Responsive Bolaform Supra-Amphiphile

An amylase-responsive bolaform supra-amphiphile was constructed by the complexation between β-cyclodextrin and a bolaform covalent amphiphile on the basis of host–guest interaction. The bolaform covalent amphiphile could self-assemble in solution, forming sheet-like aggregates and displaying weak fluorescence because of aggregation-induced quenching. The addition of β-cyclodextrin led to the formation of the bolaform supra-amphiphile, prohibiting the aggregation of the bolaform covalent amphiphile and accompanying with the significant recovery of fluorescence. Upon the addition of α-amylase, with the degradation β-cyclodextrin, the fluorescence of the supra-amphiphile would quench gradually and significantly, and the quenching rate linearly correlated to the concentration of α-amylase. This study enriches the field of supra-amphiphiles on the basis of noncovalent interactions, and moreover, it may provide a facile way to estimate the activity of α-amylase

Controllable Supramolecular Polymerization Promoted by Host-Enhanced Photodimerization

In this letter, we report a new method of controllable supramolecular polymerization, taking advantage of host-enhanced photodimerization. The low-molecular-weight supramolecular oligomers were formed by noncovalent complexation between cucurbit[8]­urils (CB[8]) and the bifunctional monomers (DBN) with Brooker’s merocyanine moiety (MOED) on either end. Interestingly, when irradiated with UV light, the supramolecular oligomers could transform into supramolecular polymers with high molecular weight. The molecular weight of supramolecular polymers could be controlled by varying the irradiation time. It is highly anticipated that this work can enrich the methods on the modulation of supramolecular polymerization