Design of Vanadium Complex Catalysts for Precise Olefin Polymerization

Amorphous Elastomeric Ultra-High Molar Mass Polypropylene in High Yield by Half-Titanocene Catalysts

Propylene polymerizations with different ketimide-modified half-titanocene catalysts, Cp'TiCl2(N=CtBu2) [Cp' = C5H5 (1), C5Me5 (2), Me3SiC5H4 (3)], with MAO as a cocatalyst, were investigated. The obtained polymers were studied in detail by determining their microstructure, molar masses, thermal, and mechanical properties. The Cp*-ketimide, (C5Me5)TiCl2(N=CtBu2) (2), exhibited higher catalytic activities than Cp'TiCl2(N=CtBu2) (1,3), yielding higher molar mass polymers, Mw up to 1400 Kg/mol. All the synthesized polypropylenes (PP) are atactic and highly regioregular, with predominant rrrr pentads, especially PP prepared with catalyst 1. Differential scanning calorimetry (DSC) established that the polymers are fully amorphous aPP, and no melting endotherm events are detected. Glass transition temperatures were detected between -2 and 2 °C. These polypropylenes have been established to be high-performance thermoplastic elastomers endowed with remarkably high ductility, and a tensile strain at break higher than 2000%.

Vanadium-catalysed regioselective hydroboration of epoxides for synthesis of secondary alcohols

Regioselective epoxide ring-opening through hydroboration catalysed by a vanadium(III) dialkyl complex supported by a redox-active terpyridine ligand is reported. Secondary alcohols were obtained in high yields via effective Markovnikov hydroboration of terminal epoxides, showcasing a new catalytic application of an earth-abundant vanadium(III) complex.

Transition Metal-(μ-Cl)-Aluminum Bonding in α-Olefin and Diene Chemistry

Olefin and diene transformations, catalyzed by organoaluminum-activated metal complexes, are widely used in synthetic organic chemistry and form the basis of major petrochemical processes. However, the role of M−(μ-Cl)−Al bonding, being proven for certain >C=C< functionalization reactions, remains unclear and debated for essentially more important industrial processes such as oligomerization and polymerization of α-olefins and conjugated dienes. Numerous publications indirectly point at the significance of M−(μ-Cl)−Al bonding in Ziegler−Natta and related transformations, but only a few studies contain experimental or at least theoretical evidence of the involvement of M−(μ-Cl)−Al species into catalytic cycles. In the present review, we have compiled data on the formation of M−(μ-Cl)−Al complexes (M = Ti, Zr, V, Cr, Ni), their molecular structure, and reactivity towards olefins and dienes. The possible role of similar complexes in the functionalization, oligomerization and polymerization of α-olefins and dienes is discussed in the present review through the prism of the further development of Ziegler−Natta processes and beyond.

Dipicolinate Complexes of Oxovanadium(IV) and Dioxovanadium(V) with 2-Phenylpyridine and 4,4'-Dimethoxy-2,2'-bipyridyl as New Precatalysts for Olefin Oligomerization

Polyolefins are used in everyday life, including in the production of many types of plastic. In addition, polyolefins account for over 50% of the polymers produced in the world. After conducting the oligomerization reactions of 2-propen-1-ol, 2-chloro-2-propen-1-ol, and norborene, polyolefins are obtained. In this report, two complexes of oxovanadium(IV) and dioxovanadium(V) with dipicolinate, 2-phenylyridine, and 4,4'-dimethoxy-2,2'-bipyridyl as precatalysts for 2-propen-1-ol, 2-chloro-2-propen-1-ol, and norborene oligomerizations are prepared. We present for the first time the new dipicolinate complex compound of oxovanadium(IV) with 4,4'-dimetoxy-2,2'-bipyridyl. Both complexes were tested for catalytic activity in the oligomerization reactions of 2-propen-1-ol, 2-chloro-2-propen-1-ol, and norbornene. Both synthesized complexes showed high catalytic activity in these oligomerization reactions, except for the oligomerization of norbornene.

Solution XAS Analysis for Reactions of Phenoxide-Modified (Arylimido)vanadium(V) Dichloride and (Oxo)vanadium(V) Complexes with Al Alkyls: Effect of Al Cocatalyst in Ethylene (Co)polymerization

V K-edge XANES (XANES = X-ray Absorption Near Edge Structure) spectra of the reaction solution of V(NAr)Cl2(OAr) (1, Ar = 2,6-Me2C6H3) with halogenated Al alkyls (Me2AlCl, Et2AlCl, EtAlCl2, 50 equiv) in toluene showed low energy shifts (2.6–3.6 eV on the basis of inflection point in the photon energy) in the edge absorption accompanying slight shift to low photon energy in the pre-edge peak (λmax values); a similar spectrum was observed when the reaction of 1 with Me2AlCl was conducted in n-hexane. These results strongly suggest a formation of similar vanadium(III) species irrespective of kind of Al alkyls and solvent (toluene or n-hexane). Significant low-energy shifts in the edge absorption accompanied with diminishing the strong pre-edge absorption were also observed when VOCl3 or VO(OiPr)3 was treated with Me2AlCl (10 equiv) in toluene, clearly indicating a formation of low oxidation state vanadium species accompanied with certain structural changes (from tetrahedral to octahedral) in solution.

Design and synthesis of binuclear vanadium catalysts for copolymerization of ethylene and polar monomers

Binuclear vanadium complexes exhibited higher activity than monometallic complexes in ethylene polymerization and afforded UHMWPE. The binuclear catalysts also showed moderate activity in copolymerization with 10-undecen-1-ol and methyl 10-undecenoate.

Copolymerization of Ethylene with Selected Vinyl Monomers Catalyzed by Group 4 Metal and Vanadium Complexes with Multidentate Ligands: A Short Review

This paper gives a short overview of homogeneous post-metallocene catalysts based on group 4 metal and vanadium complexes bearing multidentate ligands. It summarizes the catalytic behavior of those catalysts in copolymerization of ethylene with 1-olefins, with styrenic monomers and with α,ω-alkenols. The review is focused on finding correlations between the structure of a complex, its catalyst activity and comonomer incorporation ability, as well as the microstructure of the copolymer chains.

Effect of para-Substituents in Ethylene Copolymerizations with 1-Decene, 1-Dodecene, and with 2-Methyl-1-Pentene Using Phenoxide Modified Half-Titanocenes-MAO Catalyst Systems

Effect of para-substituents in the ethylene (E) copolymerization with 1-decene (DC), 1-dodecene (DD), and with 2-methyl-1-pentene (2M1P) using a series of Cp*TiCl2 (O-2,6-i Pr2 -4-R-C6 H2 ) [R=H (1), t Bu (2), Ph (3), CHPh2 (4), CPh3 (5), SiMe3 (6), SiEt3 (7), and newly prepared 4-t BuC6 H4 (8) and 3,5-Me2 C6 H3 (9)]-MAO catalyst systems has been studied. The activities in these copolymerization reactions were affected by the para-substituent, and the SiMe3 (6), SiEt3 (7) and 3,5-Me2 C6 H3 (9) analogues showed the higher activities at 50 °C in the E copolymerization reactions with DC (1.06-1.44×106  kg-polymer/mol-Ti⋅h), DD (1.04-1.88×106  kg-polymer/mol-Ti⋅h) than the others, whereas no significant differences were observed in the comonomer incorporations. Complexes 6 and 7 also showed the higher activities at 50 °C in the E/2M1P copolymerization, and the 2M1P incorporation was affected by the para-substituent and the polymerization temperature; complex 9 showed better 2M1P incorporation at 25 °C.

A highly chlorinated xylene promoter for ethylene-propylene copolymerisation over a vanadium catalyst

The regularities of ethylene-propylene copolymerisation over a vanadium oxytrichloride (VOCl₃)-ethylaluminium sesquichloride (EASC) catalytic system in the presence of hexachloro-p-xylene (HCPX), tert-butyl chloride, trichlorotoluene, hexachlorocyclopentadiene, and trichloroacetate were studied. The main kinetic regularities of ethylene-propylene copolymerisation when using HCPX were determined and the kinetic parameters of the process were obtained. It was shown that hexachloro-p-xylene is the most efficient promoter of polymerisation that increases activity of the "vanadium" catalyst severalfold and enhances propylene reactivity in its copolymerisation with ethylene. A number of molecular characteristics and physicochemical parameters were determined for the synthesised samples of ethylene-propylene copolymers. The resulting copolymers have a higher molecular weight and a broad molecular weight distribution and are richer in propylene monomers compared to the copolymers synthesised in the catalytic system without HCPX. Modification of the "vanadium" catalyst yields the copolymer with a more homogeneous structure. Assumptions were made about the mechanism of action of the promoter under study in the VOCl₃-EASC catalytic system.

A benzene-bridged divanadium complex-early transition metal catalyst for alkene alkylarylation with PhI(O2CR)2via decarboxylation

The synthesis, structure and catalytic activity of a benzene-bridged divanadium complex were comprehensively studied. The reduction of (Nacnac)VCl2 (1) (Nacnac = (2,6-iPr2C6H3NCMe)2HC) supported by β-diketiminate with potassium graphite (KC8) by employing benzene as the solvent allows access to the benzene-bridged inverted-sandwich divanadium complex (μ-η6:η6-C6H6)[V(Nacnac)]2 (2a), which can catalyze alkene alkylarylation with hypervalent iodine(iii) reagents (HIRs) via decarboxylation to generate regioselectively diverse indolinones. Furthermore, the mild nature of this reaction was amenable to a wide range of functionalities on alkenes and HIRs. Mechanistic studies revealed a relay sequence of decarboxylative radical alkylation/radical arylation/oxidative re-aromatization.

Binary and Ternary Vanadium Oxides: General Overview, Physical Properties, and Photochemical Processes for Environmental Applications

This review article is a comprehensive report on vanadium oxides which are interesting materials for environmental applications. Therefore, a general overview of vanadium and its related oxides are presented in the first two parts. Afterwards, the physical properties of binary and ternary vanadium oxides in single and mixed valence states are described such as their structural, optical, and electronic properties. Finally, the use of these vanadium oxides in photochemical processes for environmental applications is detailed, especially for the production of hydrogen by water splitting and the degradation of organic pollutants in water using photocatalytic and photo-Fenton processes. The scientific aim of such a review is to bring a comprehensive tool to understand the photochemical processes triggered by vanadium oxide based materials where the photo-induced properties are thoroughly discussed based on the detailed description of their intrinsic properties.

Highly efficient terpolymerizations of ethylene/propylene/ENB with a half-titanocene catalytic system

Highly efficient terpolymerization of ethylene, propylene and 5-ethylidene-2-norbornene using a half-titanocene containing iminoimidazolidine with methylaluminoxane/Al(iBu)3/2,6-ditertbutyl-4-methyl-phenol was achieved.

Highly 2,3-selective polymerization of phenylallene and its derivatives by vanadium complexes

Allene polymerizations by vanadium complexes using various Al co-catalysts were carried out. All the vanadium complexes show moderate activity for phenylallene and high 2,3-selectivity (>99%).

Synthesis of ethylene–norbornene–1-octene terpolymers with high 1-octene contents, molar masses, and tunable Tg values, in high yields using half-titanocene catalysts

Synthesis of unique poly(E-ter–N-ter–O)s using half-titanocene catalysts: 1-octene does not behave as a chain termination/transfer agent unlike ansa-metallocenes.

Structural and Thermal Properties of Ethylene-Norbornene Copolymers Obtained Using Vanadium Homogeneous and SIL Catalysts

The series of ethylene-norbornene (E-NB) copolymers was obtained using different vanadium homogeneous and supported ionic liquid (SIL) catalyst systems. The ¹³C and ¹H NMR (carbon and proton nuclear magnetic resonance spectroscopy) together with differential scanning calorimetry (DSC) were applied to determine the composition of copolymers such as comonomer incorporation (C_NB), monomer dispersity (MD), monomer reactivity ratio (r_e), sequence length of ethylene (l_e) and tetrad microblock distributions. The relation between the type of catalyst, reaction conditions and on the other hand, the copolymer microstructure, chain termination reaction analyzed by the type of unsaturation are discussed. In addition, the thermal properties of E-NB copolymers such as the melting and crystallization behavior, like also the heterogeneity of composition described by successive the self-nucleation and annealing (SSA) and the dispersity index (DI) were determined.

The Effect of SiMe3 and SiEt3 Para Substituents for High Activity and Introduction of a Hydroxy Group in Ethylene Copolymerization Catalyzed by Phenoxide-Modified Half-Titanocenes

Remarkable effects of SiMe₃ and SiEt₃ para-substituents in the phenoxide-modified half-titanocenes, Cp*TiCl₂ (O-2,6-ⁱ Pr₂ -4-R-C₆ H₂ ) [R=SiMe₃ (6), SiEt₃ (7)], toward the catalytic activities in ethylene copolymerizations with 2-methyl-1-pentene, 1-decene, 1-dodecene and with 9-decen-1-ol (DC-OH) have been demonstrated. The activities by 6, 7 at 50 °C showed higher than those conducted at 25 °C in all cases in the presence of MAO cocatalyst. Efficient synthesis of high-molecular-weight (HMW) ethylene copolymers incorporating DC-OH (or 5-hexen-1-ol, HX-OH) has been attained in the copolymerization by 7, which showed better DC-OH (HX-OH) incorporation at 50 °C to afford the HMW copolymers, poly(ethylene-co-DC-OH)s, with high activities (activity 1.21-3.81×10⁵  kg-polymer mol^-1 -Ti h, M_n =6.55-10.0×10⁴ , DC-OH 2.3-3.6 mol %).

Electrochemical Selective Recovery of Heavy Metal Vanadium Oxyanion from Continuously Flowing Aqueous Streams

An electrochemical flow cell with redox-active electrodes was used for selective removal and recovery of vanadium(V) oxyanions from aqueous streams. The cell relies on intrinsic affinity of the redox-active polymer poly(vinyl)ferrocene (PVFc) and demonstrates selectivity of >10 towards vanadium compared to a background electrolyte in 40-fold abundance. We demonstrate highly selective vanadium removal in the presence of various competing anions (i.e., fluoride, bromide, nitrate, and sulfate). Surface elemental analysis reveals significant correlation between PVFc moieties and vanadium-rich regions after adsorption, corroborating the central role of PVFc modulation on vanadium separation. We further propose a vanadium speciation mechanism in which high and low pH environments during adsorption and desorption steps favor formation of, respectively, H2 VO3 - / HVO4 2- and H2 VO3 - / H3 VO4 / VO2 + . Results have implications for the development and optimization of flow devices, as per our observations, excessively low pH environments during desorption can lead to subsequent re-adsorption of cationic vanadium(V).

Solution XANES and EXAFS analysis of active species of titanium, vanadium complex catalysts in ethylene polymerisation/dimerisation and syndiospecific styrene polymerisation

Mechanistic studies in homogeneous catalysis through the solution transition metal K Edge XANES (X-ray absorption near-edge structure) and EXAFS (Extended X-ray absorption fine structure) analysis for vanadium and titanium complex catalysts for ethylene polymerisation/dimerization, and syndiospecific styrene polymerisation, including interpretation of the XANES spectra, have been introduced. The core excitation spectra of the complexes based on the time-dependent density functional theory (TD-DFT) can be used to interpret the Ti and V K-edge features and to extract information on the electronic structure from the XANES spectra. Theoretical calculations and experimental XAS analysis should have great potential for analysing the active species.