Novel Polyaromatic Quinone Imines. 2. Synthesis of Model Compounds and Stereoregular Poly(quinone imines) from Disubstituted Anthraquinones

Novel poly(quinone diimines) from anthraquinones symmetrically disubstituted with solubilizing ethyleneoxy or long chain alkoxy groups have been synthesized and characterized. The disubstituted anthraquinones 1,5-bis(2-methoxyethoxy)anthraquinone (EO1AQ), 1,5-bis(2-(2-methoxyethoxy)ethoxy)anthraquinone (EO2AQ), 1,5-bis(2-(2-(2-methoxyethoxy)ethoxy)anthraquinone (EO2AQ), 1,5-bis(2-(2-2-methoxyethoxy)ethoxy)ethoxy)anthraquinone (EO3AQ), 1,5-bis(octyloxy)anthraquinone (15OOAQ), 2,6-bis(octyloxy)anthraquinone (26OOAQ), and 1,4-bis(octyloxy)anthraquinone (14OOAQ) were synthesized and condensed with aniline in the presence of titanium tetrachloride and 1,4-diazabicyclo[2.2.2]octane to give N,N‘-diphenyl-1,5-bis(2-methoxyethoxy)nanthraquinone 9,10-diimine (DEOnAQ, n = 1−3), N,N-diphenyl-1,5-bis(octyloxy)anthraquinone 9,10-diimine (15DOOAQ), and N,N‘-diphenyl-2,6-bis(octyloxy)anthraquinone 9,10-diimine (26DOOAQ), respectively, as model compounds for the polymers. The relative stereochemistry of these diimines was determined by 1H NMR spectroscopy. Polycondensation of the disubstituted anthraquinones with 4,4‘-thiodianiline (SDA) gave high molecular weight (Mw 30 000) poly(anthraquinone diimines) and large macrocycles. Polycondensation of 1,4-phenylenediamine (PDA) with EO2AQ gave high molecular weight (Mw 14 000) polyaromatic anthraquinone diimines. PDA gave molecular weights of Mw 5000−23 000 for the bis(octyloxy)-substituted anthraquinones. The molecular weights of polymerizations incorporating PDA are lowered due to steric interactions of successive repeat units and solubility constraints

Polypropylene “Chain Shuttling” at Enantiomorphous and Enantiopure Catalytic Species: Direct and Quantitative Evidence from Polymer Microstructure

Polypropylene “Chain Shuttling” at Enantiomorphous and Enantiopure Catalytic Species:  Direct and Quantitative Evidence from Polymer Microstructur

Stereoregular Poly(benzoquinone imines) from Methyl-Substituted Benzoquinones

Stereoregular Poly(benzoquinone imines) from Methyl-Substituted Benzoquinone

Copolymerization Studies of Vinyl Chloride and Vinyl Acetate with Ethylene Using a Transition-Metal Catalyst

Since the advent of Ziegler−Natta polymerization of ethylene, attempts have been made to extend coordination polymerization to commercially important monomers with polar functionality. In this study we examined the copolymerization of perdeuterated vinyl chloride (VC) and perdeuterated vinyl acetate (VA) with ethylene using a tridentate Fe(II) dichloride pyridine diimine metal catalyst. The resulting ethylene oligomers were examined by GC/MS and 2H NMR spectroscopy. It was shown that VC was inserted once for every ∼180 ethylene monomers and VA was inserted once for every ∼350 ethylene monomers. VC and VA behave as comonomers for coordination/insertion polymerizations with ethylene. However, we find that insertion with either monomer leads to termination of the growing chain via β-elimination processes. The deuterium atoms are exclusively located at the olefin terminus for each of the monomers

Intra- and Intermolecular NMR Studies on the Activation of Arylcyclometallated Hafnium Pyridyl-Amido Olefin Polymerization Precatalysts

Pyridyl-amido catalysts have emerged recently with great promise for olefin polymerization. Insights into the activation chemistry are presented in an initial attempt to understand the polymerization mechanisms of these important catalysts. The activation of C1-symmetric arylcyclometallated hafnium pyridyl-amido precatalysts, denoted Me2Hf{N−,N,C−} (1, aryl = naphthyl; 2, aryl = phenyl), with both Lewis (B(C6F5)3 and [CPh3][B(C6F5)4]) and Brønsted ([HNR3][B(C6F5)4]) acids is investigated. Reactions of 1 with B(C6F5)3 lead to abstraction of a methyl group and formation of a single inner-sphere diastereoisomeric ion pair [MeHf{N−,N,C−}][MeB(C6F5)3] (3). A 1:1 mixture of the two possible outer-sphere diastereoisomeric ion pairs [MeHf{N−,N,C−}][B(C6F5)4] (4) is obtained when [CPh3][B(C6F5)4] is used. [HNR3][B(C6F5)4] selectively protonates the aryl arm of the tridentate ligand in both precatalysts 1 and 2. A remarkably stable [Me2Hf{N−,N,C2}][B(C6F5)4] (5) outer-sphere ion pair is formed when the naphthyl substituent is present. The stability is attributed to a hafnium/η2-naphthyl interaction and the release of an eclipsing H−H interaction between naphthyl and pyridine moieties, as evidenced through extensive NMR studies, X-ray single crystal investigation and DFT calculations. When the aryl substituent is phenyl, [Me2Hf{N−,N,C2}][B(C6F5)4] (10) is originally obtained from protonation of 2, but this species rapidly undergoes remetalation, methane evolution, and amine coordination, giving a diastereomeric mixture of [MeHf{N−,N,C−}NR3][B(C6F5)4] (11). This species transforms over time into the trianionic-ligated [Hf{N−,C−,N,C−}NR3][B(C6F5)4] (12) through activation of a C−H bond of an amido-isopropyl group. In contrast, ion pair 5 does not spontaneously undergo remetalation of the naphthyl moiety; it reacts with NMe2Ph leading to [MeHf{N−,N}NMe2C6H4][B(C6F5)4] (7) through ortho-metalation of the aniline. Ion pair 7 successively undergoes a complex transformation ultimately leading to [Hf{N−,C−,N,C−}NMe2Ph][B(C6F5)4] (8), strictly analogous to 12. The reaction of 5 with aliphatic amines leads to the formation of a single diastereomeric ion pair [MeHf{N−,N,C−}NR3][B(C6F5)4] (9). These differences in activation chemistry are manifested in the polymerization characteristics of these different precatalyst/cocatalyst combinations. Relatively long induction times are observed for propene polymerizations with the naphthyl precatalyst 1 activated with [HNMe3Ph][B(C6F5)4]. However, no induction time is present when 1 is activated with Lewis acids. Similarly, precatalyst 2 shows no induction period with either Lewis or Brønsted acids. Correlation of the solution behavior of these ion pairs and the polymerization characteristics of these various species provides a basis for an initial picture of the polymerization mechanism of these important catalyst systems

Intra- and Intermolecular NMR Studies on the Activation of Arylcyclometallated Hafnium Pyridyl-Amido Olefin Polymerization Precatalysts

Pyridyl-amido catalysts have emerged recently with great promise for olefin polymerization. Insights into the activation chemistry are presented in an initial attempt to understand the polymerization mechanisms of these important catalysts. The activation of C1-symmetric arylcyclometallated hafnium pyridyl-amido precatalysts, denoted Me2Hf{N−,N,C−} (1, aryl = naphthyl; 2, aryl = phenyl), with both Lewis (B(C6F5)3 and [CPh3][B(C6F5)4]) and Brønsted ([HNR3][B(C6F5)4]) acids is investigated. Reactions of 1 with B(C6F5)3 lead to abstraction of a methyl group and formation of a single inner-sphere diastereoisomeric ion pair [MeHf{N−,N,C−}][MeB(C6F5)3] (3). A 1:1 mixture of the two possible outer-sphere diastereoisomeric ion pairs [MeHf{N−,N,C−}][B(C6F5)4] (4) is obtained when [CPh3][B(C6F5)4] is used. [HNR3][B(C6F5)4] selectively protonates the aryl arm of the tridentate ligand in both precatalysts 1 and 2. A remarkably stable [Me2Hf{N−,N,C2}][B(C6F5)4] (5) outer-sphere ion pair is formed when the naphthyl substituent is present. The stability is attributed to a hafnium/η2-naphthyl interaction and the release of an eclipsing H−H interaction between naphthyl and pyridine moieties, as evidenced through extensive NMR studies, X-ray single crystal investigation and DFT calculations. When the aryl substituent is phenyl, [Me2Hf{N−,N,C2}][B(C6F5)4] (10) is originally obtained from protonation of 2, but this species rapidly undergoes remetalation, methane evolution, and amine coordination, giving a diastereomeric mixture of [MeHf{N−,N,C−}NR3][B(C6F5)4] (11). This species transforms over time into the trianionic-ligated [Hf{N−,C−,N,C−}NR3][B(C6F5)4] (12) through activation of a C−H bond of an amido-isopropyl group. In contrast, ion pair 5 does not spontaneously undergo remetalation of the naphthyl moiety; it reacts with NMe2Ph leading to [MeHf{N−,N}NMe2C6H4][B(C6F5)4] (7) through ortho-metalation of the aniline. Ion pair 7 successively undergoes a complex transformation ultimately leading to [Hf{N−,C−,N,C−}NMe2Ph][B(C6F5)4] (8), strictly analogous to 12. The reaction of 5 with aliphatic amines leads to the formation of a single diastereomeric ion pair [MeHf{N−,N,C−}NR3][B(C6F5)4] (9). These differences in activation chemistry are manifested in the polymerization characteristics of these different precatalyst/cocatalyst combinations. Relatively long induction times are observed for propene polymerizations with the naphthyl precatalyst 1 activated with [HNMe3Ph][B(C6F5)4]. However, no induction time is present when 1 is activated with Lewis acids. Similarly, precatalyst 2 shows no induction period with either Lewis or Brønsted acids. Correlation of the solution behavior of these ion pairs and the polymerization characteristics of these various species provides a basis for an initial picture of the polymerization mechanism of these important catalyst systems