RESUMEN
Modern industry of advanced polyolefins extensively uses Group 4 metallocene and post-metallocene catalysts. High-throughput polyolefin technologies demand the use of heterogeneous catalysts with a given particle size and morphology, high thermal stability, and controlled productivity. Conventional Group 4 metal single-site heterogeneous catalysts require the use of high-cost methylalumoxane (MAO) or perfluoroaryl borate activators. However, a number of inorganic phases, containing highly acidic Lewis and Brønsted sites, are able to activate Group 4 metal pre-catalysts using low-cost and affordable alkylaluminums. In the present review, we gathered comprehensive information on MAO- and borate-free activating supports of different types and discussed the surface nature and chemistry of these phases, examples of their use in the polymerization of ethylene and α-olefins, and prospects of the further development for applications in the polyolefin industry.
RESUMEN
A series of potassium salts of di- and tri-arylsubstituted cyclopentadienes has been obtained by the metalation of the corresponding cyclopentadienes with benzylpotassium in THF media. Crystals of all compounds, afforded by recrystallization from THF/hexane, diglyme-THF/hexane and toluene/hexane mixtures, have been studied by X-ray diffraction. All studied potassium cyclopentadienides exhibit the luminescence at room temperature and overall quantum yield of photoluminescence for potassium salt of diarylsubstituted cyclopentadiene is 18%.
RESUMEN
Biodegradable polyesters represent an advanced alternative to polyolefin plastics in various applications. Polybutylene adipate terephthalate (PBAT) can compete with polyolefins in terms of their mechanical characteristics and melt processing conditions. The properties of PBAT depend on the molecular weight, dispersity, and architecture of the copolymer. Long-chain branching (LCB) of the PBAT backbone is an efficient method for the improvement of the copolymer characteristics. In the present work, we studied branching agents (BAs) 1-7 of different structures in the two-stage polycondensation of 1,4-butanediol, dimethyl terephthalate, and adipic acid and investigated the composition and melt rheology of the copolymers. According to the results of the research, 1,1,1-tris(hydroxymethyl)ethane 2 and 3-hydroxy-2-(hydroxymethyl)-2-methylpropanoic acid 5 outperformed glycerol 1 as BAs in terms of shear thinning behavior and viscoelasticity.
RESUMEN
The crystal structures of three unusual chromium organophosphate complexes have been determined, namely, bis(µ-butyl 2,6-di-tert-butyl-4-methylphenyl hydrogen phosphato-κO:κO')di-µ-hydroxido-bis[(butyl 2,6-di-tert-butyl-4-methylphenyl hydrogen phosphato-κO)(butyl 2,6-di-tert-butyl-4-methylphenyl phosphato-κO)chromium](Cr-Cr) heptane disolvate or {Cr2(µ2-OH)2[µ2-PO2(OBu)(O-2,6-tBu2-4-MeC6H2)-κO:κO']2[PO2(OBu)(O-2,6-tBu2-4-MeC6H2)-κO]2[HOPO(OBu)(O-2,6-tBu2-4-MeC6H2)-κO]2}·2C7H16, [Cr2(C19H32O4P)4(C19H33O4P)2(OH)2]·2C7H16, denoted (1)·2(heptane), [µ-bis(2,6-diisopropylphenyl) phosphato-1κO:2κO']bis[bis(2,6-diisopropylphenyl) phosphato]-1κO,2κO-chlorido-2κCl-triethanol-1κ2O,2κO-di-µ-ethanolato-1κ2O:2κ2O-dichromium(Cr-Cr) ethanol monosolvate or {Cr2(µ2-OEt)2[µ2-PO2(O-2,6-iPr2-C6H3)2-κO:κO'][PO2(O-2,6-iPr2-C6H3)2-κO]2Cl(EtOH)3}·EtOH, [Cr2(C2H5O)2(C24H34O4P)3Cl(C2H6O)3]·C2H6O, denoted (2)·EtOH, and di-µ-ethanolato-1κ2O:2κ2O-bis{[bis(2,6-diisopropylphenyl) hydrogen phosphato-κO][bis(2,6-diisopropylphenyl) phosphato-κO]chlorido(ethanol-κO)chromium}(Cr-Cr) benzene disolvate or {Cr2(µ2-OEt)2[PO2(O-2,6-iPr2-C6H3)2-κO]2[HOPO(O-2,6-iPr2-C6H3)2-κO]2Cl2(EtOH)2}·2C6H6, [Cr2(C2H5O)2(C24H34O4P)2(C24H35O4P)2Cl2(C2H6O)2]·2C6H6, denoted (3)·2C6H6. Complexes (1)-(3) have been synthesized by an exchange reaction between the in-situ-generated corresponding lithium or potassium disubstituted phosphates with CrCl3(H2O)6 in ethanol. The subsequent crystallization of (1) from heptane, (2) from ethanol and (3) from an ethanol/benzene mixture allowed us to obtain crystals of (1)·2(heptane), (2)·EtOH and (3)·2C6H6, whose structures have the monoclinic P21, orthorhombic P212121 and triclinic P-1 space groups, respectively. All three complexes have binuclear cores with a single Cr-Cr bond, i.e. Cr2O6P2 in (1), Cr2PO4 in (2) and Cr2O2 in (3), where the Cr atoms are in distorted octahedral environments, formally having 16 e per Cr atom. The complexes have bridging ligands µ2-OH in (1) or µ2-OEt in (2) and (3). The organophosphate ligands demonstrate terminal κO coordination modes in (1)-(3) and bridging µ2-κO:κO' coordination modes in (1) and (2). All the complexes exhibit hydrogen bonding: two intramolecular Ophos...H-Ophos interactions in (1) and (3) form two {H[PO2(OR)2]2} associates; two intramolecular Cl...H-OEt hydrogen bonds additionally stabilize the Cr2O2 core in (3); two intramolecular Ophos...H-OEt interactions and two O...H-O intermolecular hydrogen bonds with a noncoordinating ethanol molecule are observed in (2)·EtOH. The presence of both basic ligands (OH- or OEt-) and acidic [H(phosphate)2]- associates at the same metal centres in (1) and (3) is rather unusual. Complexes may serve as precatalysts for ethylene polymerization under mild conditions, providing polyethylene with a small amount of short-chain branching. The formation of a small amount of α-olefins has been detected in this reaction.
RESUMEN
The data presented in this paper are related to the research article entitled "Mechanistic study of transesterification in TBD-catalyzed ring-opening polymerization of methyl ethylene phosphate" (Nifant'ev et al., 2019). In this data article, we present 3D molecular information of 76 structures for TBD-catalyzed transformations of methyl ethylene phosphate (MeOEP) and trimethyl phosphate (TMP). We also present 3D molecular information for 24 complexes that model the reaction profile of transesterification of poly(MeOEP) and TMP catalyzed by 2,6-di-tert-butyl-4-methylphenoxy magnezium species, complementing the article "Mechanistic insights of BHT-Mg-catalyzed ethylene phosphate's coordination ring-opening polymerization: DFT modeling and experimental data" (Nifant'ev et al., 2018). The data contains stationary points and transition states (TS) along the first propagation step of MeOEP ring-opening polymerization (ROP) for alternative amide and donor-acceptor mechanisms, initiated by EtOH in the presence of TBD; stationary points and TS for MeOH and HOCH2CH2OP(O)(OMe)2 initiated ROP of MeOEP; and stationary points and TS for transesterification of poly(MeOEP) and TMP. In addition, the data contains stationary points and transition states for the ROP of MeOEP and transesterification of poly(MeOEP) and TMP catalyzed by 2,6-di-tert-butylphenoxy magnesium complex. The data are provided in a PDB format that can be used for further studies.
RESUMEN
The solvated centrosymmmtric title compound, [Li2(C24H34O4P)2(C10H8N2)2]·2C7H8, was formed in the reaction between {Li[(2,6-iPr2C6H3-O)2POO](MeOH)3}(MeOH) and 2,2'-bi-pyridine (bipy) in toluene. The structure has monoclinic (P21/n) symmetry at 120â K and the asymmetric unit consists of half a complex mol-ecule and one mol-ecule of toluene solvent. The diaryl phosphate ligand demonstrates a µ-κO:κO'-bridging coordination mode and the 2,2'-bi-pyridine ligand is chelating to the Li+ cation, generating a distorted tetra-hedral LiN2O2 coordination polyhedron. The complex exhibits a unique dimeric Li2O4P2 core. One isopropyl group is disordered over two orientations in a 0.621â (4):0.379â (4) ratio. In the crystal, weak C-Hâ¯O and C-Hâ¯π inter-actions help to consolidate the packing. Catalytic systems based on the title complex and on the closely related complex {Li[(2,6-iPr2C6H3-O)2POO](MeOH)3}(MeOH) display activity in the ring-opening polymerization of ∊-caprolactone and l-dilactide.
RESUMEN
Reductive cyclization of 1,3,5-triphenyl- and 3-(2-meth-oxy-phen-yl)-1,5-di-phenyl-pentane-1,5-diones by zinc in acetic acid medium leads to the formation of 1,2,4-tri-phenyl-cyclo-pentane-1,2-diol [1,2,4-Ph3C5H5-1,2-(OH)2, C23H22O2, (I)] and 4-(2-meth-oxy-phen-yl)-1,2-di-phenyl-cyclo-pentane-1,2-diol [4-(2-MeOC6H4)-1,2-Ph2C5H5-1,2-(OH)2, C24H24O3, (II)]. Their single crystals have been obtained by crystallization from a THF/hexane solvent mixture. Diols (I) and (II) crystallize in ortho-rhom-bic (Pbca) and triclinic (P ) space groups, respectively, at 150â K. Their asymmetric units comprise one [in the case of (I)] and three [in the case of (II)] crystallographically independent mol-ecules of the achiral (1R,2S,4r)-diol isomer. Each hydroxyl group is involved in one intra-molecular and one inter-molecular O-Hâ¯O hydrogen bond, forming one-dimensional chains. Compounds (I) and (II) have been used successfully as precatalyst activators for the ring-opening polymerization of ∊-caprolactone.
RESUMEN
Cyclopentadienides of d- and f-elements are highly important complexes with undoubted potential for practical applications. Annelation of a heterocyclic fragment with an η5-ring results in substantial improvement of the catalytic properties of these compounds, called "heterocenes"; the investigation of metal coordination with these specific ligands is a highly important problem. We prepared potassium derivatives 5-8 of heterocycle-annelated cyclopentadienes with different structures - derivatives of cyclopenta[1,2-b:4,3-b']dithiophene (1), indeno[2,1-b]indole (2), indeno[1,2-b]indole (3), and indeno[1,2-b]indolizine (4) and studied the crystal and molecular structures of these salts by X-ray diffraction. We found that heterocycle-fused cyclopentadienides demonstrate remarkable diversity in metal-ligand coordination modes and crystal packing, with formation of two-dimensional polymeric (5), linear polymeric (6), tetrameric (7) and monomeric (8) structures. The NMR spectral data and results of DFT modeling indicate an increase in electron density in the cyclopentadienyl fragment, and this effect was found to be larger in the derivative of the new indolizine ligand precursor 4. The results of our study will be used in the design of next-generation catalysts of α-olefin polymerization.