Aqueous Poly(arylacetylene) Dispersions

Aqueous poly(phenylacetylene) dispersions were obtained by catalytic polymerization in emulsion with a phosphine-modified Pd(II) catalyst. A range of mono- and bidentate phosphines were screened. A tBu2P(CH2)3PtBu2-modified catalyst exhibits very high rates up to 2 × 105 TO h−1 (TO = moles of monomer converted per mole of metal present in the reaction mixture) in the preparation of colloidally stable poly(phenylacetylene) dispersions. Polymerization in miniemulsion afforded dispersions with up to 36 wt % solids content and average particle sizes of ca. 130 nm. From microemulsions dispersions with ca. 25 nm particle size were obtained

Nanoparticles from Step-Growth Coordination Polymerization

Nanoparticles from Step-Growth Coordination Polymerizatio

Highly Active Binuclear Neutral Nickel(II) Catalysts Affording High Molecular Weight Polyethylene

A series of new binuclear neutral κ2-N,O-chelated Ni(II) complexes [(H2C)n{[(2,6-R2-4-yl-C6H2)-NC(H)-(3,5-I2-2-O-C6H2)-κ2-N,O]Ni(CH3)(pyridine)}2] (R = iPr, 3,5-(CF3)2C6H3; n = 0, 1) are reported. The complexes are single-component catalyst precursors for ethylene polymerization. Catalyst activities exceed those of mononuclear analogues studied substantially. With 3.4 × 105 TO h−1, high molecular weight polymer is obtained (Mw 9.2 × 105 g mol−1; Mn 2.8 × 105 g mol−1). Semicrystalline polyethylene with a low degree of branching is formed (2 to 12 branches/1000 carbon atoms; prepared at 30 to 70 °C polymerization temperature), with Tm 112 to 136 °C. Polymerization in aqueous emulsion affords polyethylene dispersions

Cationic Palladium η³-Allyl Complexes with Hemilabile P,O-Ligands: Synthesis and Reactivity. Insertion of Ethylene into the Pd−Allyl Function

Cationic palladium allyl complexes [(η3-C3H5)Pd(κ2P∧O)]+SbF6- (2[SbF6], P∧O ≡ Ph2P(CH2)2C(O)OEt; 3[SbF6], o-Ph2PC6H4C(O)OEt; 4[SbF6], Ph2P(CH2)2P(O)Ph2) have been prepared. In all complexes the oxygen donor can be displaced by other ligands such as carbon monoxide and ethylene. Displacement of an ester donor occurs much more readily than displacement of the phosphine oxide function. Above 0 °C, the resulting ethylene complexes [(η3-C3H5)Pd(C2H4)(κ1P∼O)]+ react to give (1,2,5-η3)-pent-1-en-5-yl complexes [(H2CCH(CH2)3Pd(κ2P∧O)]+. A rate constant of e.g. k(17 °C) = (2.27 ± 0.11) × 10-4 s-1 was determined for P,O ≡ Ph2P(CH2)2C(O)OEt by 1H NMR spectroscopy. Using 2−4 as catalyst precursors for ethylene dimerization, the allyl moiety is ultimately cleaved from the metal center as 1,4-pentadiene

Deactivation Pathways of Neutral Ni(II) Polymerization Catalysts

The novel dimethyl sulfoxide (DMSO)-coordinated complex [(N,O)Ni(CH3)(DMSO)] {1-DMSO; (N,O) = κ2-N,O-(2,6-(3,5-(F3C)2C6H3)2C6H3)−NCH−(3,5-I2-2-OC6H2)} was found to be a well-defined, very reactive precursor that enables direct observation of the activation and deactivation of neutral Ni(II) catalysts. Preparative reaction with ethylene afforded the ethyl complex [(N,O)Ni(αCH2βCH3)(DMSO)] (2-DMSO). 2-DMSO is subject to interconversion of the αC and βC moieties via an intermediate [(N,O)Ni(II)H(ethylene)] complex (this process is slow on the NMR time scale). Exposure of 1-DMSO to ethylene in DMSO solution at 55 °C results in partial reaction to form propylene (pseudo-first-order rate constant kins,Me = 6.8 ± 0.3 × 10−4 s−1 at an ethylene concentration of 0.15 M) and conversion to 2-DMSO, which catalyzes the conversion of ethylene to butenes. A relevant decomposition route of the catalyst precusor is the bimolecular elimination of ethane [ΔH⧧ = (57 ± 1) kJ mol−1 and ΔS⧧ = −(129 ± 2) J mol−1 K−1 over the temperature range 55−80 °C]. This reaction is specific to the Ni(II)−Me complex; corresponding homocoupling of the higher Ni(II)−alkyls of the propagating species in catalytic C−C linkage of ethylene was not observed, but Ni(II)−Me reacted with Ni(II)−Et to form propane, as concluded from studies with 2-DMSO and its analogue that is perdeuterated in the Ni(II)−Et moiety. Under the reaction conditions of the aforementioned catalytic C−C linkage of ethylene, additional ethane evolves from the reaction of intermediate Ni(II)−Et with Ni(II)−H. This is independently supported by reaction of 2-DMSO with the separately prepared hydride complex [(N,O)NiH(PMe3)] (3-PMe3) to afford ethane. Kinetic studies show this reaction to be bimolecular [ΔH⧧ = (47 ± 6) kJ mol−1 and ΔS⧧ = −(117 ± 15) J mol−1 K−1 over the temperature range 6−35 °C]. In contrast to these reactions identified as decomposition routes, hydrolysis of Ni(II)−alkyls by added water (D2O; H2O) occurred only to a minor extent for the Ni(II)−Me catalyst precursor, and no clear evidence of hydrolysis was observed for higher Ni(II)−alkyls. The rate of the aforementioned insertion of ethylene in 1-DMSO and the rate of catalytic ethylene dimerization are not affected by the presence of water, indicating that water also does not compete significantly with the substrate for binding sites

Polyethylenes with Combined In-Chain and Side-Chain Functional Groups from Catalytic Terpolymerization of Carbon Monoxide and Acrylate

Linear polyethylenes with a combination of incorporated in-chain keto as well as side-chain ester groups are formed by Ni(II)-catalyzed terpolymerization of ethylene, carbon monoxide, and methyl acrylate. These possess a random structure, with largely isolated nonalternating in-chain keto groups as well as ester-substituted units adjacent to the polyethylene chain, whereas the solid-state structure of polyethylene is retained. Molecular weights of the terpolymers (Mn ∼ 20.000 g mol–1) are predominantly determined by chain transfer after acrylate incorporation

Synthesis of Submicrometer Particles of a Stereoregular Polyolefin by Catalysis in Aqueous Dispersion

Synthesis of Submicrometer Particles of a Stereoregular Polyolefin by Catalysis in Aqueous Dispersio

Aqueous Dispersions of Polypropylene and Poly(1-butene) with Variable Microstructures Formed with Neutral Nickel(II) Complexes

Aqueous Dispersions of Polypropylene and Poly(1-butene) with Variable Microstructures Formed with Neutral Nickel(II) Complexe

Recoverable Catalysts Noncovalently Bound to a Hyperbranched Polyelectrolyte

Polyelectrolytes with Ph2P(C6H4-p-SO3-) counterions were prepared by ion exchange from hyperbranched polycations with a polyglycerol-based polyether scaffold and 1,2-dimethylimidazolium end groups. Upon exposing a mixture of the polyelectrolyte with [Rh(acac)(CO)2] in DMSO-d6 to 1 atm CO/H2, a large portion of the rhodium precursor is converted to [(phosphine)3Rh(H)(CO)]. Hydroformylation of 1-hexene in methanol as a model reaction proceeds with moderate activities at 80 °C, 30 bar CO/H2. The polyelectrolyte-bound catalyst was recovered by ultrafiltration and reused up to three times