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•Polyolefins are remarkable polymeric materials.•Polyolefins fit the “green polymer materials” slogan.•The newest polyolefins catalysts are post-metallocene catalysts.•The design of ...catalysts focuses on selecting metal and combining it with a ligand.•The use of transition metal catalysts, makes the polymerization processes “green”.
Polyolefins are the most widely used and needed polymers in the world. Their polymerization process is a topic of great interest among scientists. Not only do polyolefins have remarkable qualities: high strength and tensile strength, plus very good abrasion resistance, but their production process is relatively cheap and environmentally friendly. The production process of these polymers can follow a free-radical mechanism or with the use of catalysts. It is thanks to the catalysts that are used in this reaction that the polymerization can be counted among the processes that are compatible with the term “green chemistry.”
Even though metallocene catalysts were discovered as early as 1980 it is still recently, complex catalysts have received the most attention. The production technology of these catalysts and the substrate used in their synthesis allow them to be included in the group of “green catalysts.” These catalytic systems consist of a metal combined with ligands. The use of late transition metals in these systems and the choice of a suitable ligand expands their range of possibilities and applications in technology of olefin polymerizations.
This work is a review of current information on polyolefins and their “green advantages,” as well as achievements in the creation of catalysts having transition metals group.
We thank the Fonds der Chemischen Industrie (Liebig fellowship for D.M.), the German‐American Fulbright Commission (Fulbright‐Cottrell Award for D.M.) as well as the Bavarian Equal Opportunities ...Sponsorship – Realization of Equal Opportunities for Women in Research and Teaching (fellowship for A.G.) for financial support. We thank the RRZ Erlangen for computational resources.
Metal−nitrogen formally multiple bonded complexes, i. e. nitrenes, imidyls, and imido ligands, are key intermediates in organic catalysis and group transfer chemistry. Complexes of the group 9–11 metals are emerging as excellent catalysts and the isolation and characterization of these highly covalently bonded metal complexes can shed light on their structural and electronic features. Herein, we summarize the developments in the coordination chemistry of late transition metal imido‐ and nitrene complexes since 2013. Based on the computational analysis of their electronic structure, we highlight the implications on stochiometric reactivity and catalytic applications.
In this review, the key advances achieved over more than 10 years on the design and development of (imino)pyridyl transition metal complexes as catalyst precursors for the transformation of ethylene, ...higher α-olefins and cyclic olefins into either linear/branched homopolymers or oligomers are highlighted. Particular attention has been paid to the relationships between the catalytic activity exhibited by the catalysts and their electronic and geometrical structure.
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•Hybrid adsorbent was produced by grafting ethylene diamine aromatic function on silica nanoparticles.•Obtained nano adsorbent showed good capacity towards LTM and lower for ...REE.•Selectivity in both adsorption and desorption towards LTM over REE was observed.•Insights into the molecular adsorption mechanisms were obtained from molecular structures of target metal cations with the selected ligand.
Recycling of magnetic materials based on Rare Earth Elements (REE) is of major interest in the view of growing clean energy production and transportation. One of the major challenges in its realization is the need to separate smaller amounts of Late Transition Metals (LTM) from REE. Hybrid adsorbents are very attractive in finding such a solution. Here, novel silica-based nanoadsorbents were synthesized by grafting the surface of dense silica nanoparticles with a diamino functional ligand grafted via an arene linker to improve selectivity towards LTM. The produced adsorbent materials were characterized using SEM, TEM, AFM, XPS, FTIR, and TGA in its pure form and by DLS in suspension, and tested for the adsorption and separation of LTM (Co2+ and Ni2+) and REE (Sm3+ and Nd3+) in single and mixed solutions. Prepared organo-silica material showed rapid uptake of all tested cations with higher affinity towards LTM. Adsorption capacities reached values of 1.18–1.45 mmol/g for Co2+ and Ni2+, respectively, with a 1:1 metal-to-ligand stoichiometry for Ni cations. Investigation of reusability demonstrated the potential of the prepared materials as an environmentally friendly alternative in specific separation of LTM to conventional separation techniques. Investigations of the molecular structures of the Ni2+ complex with the selected molecular function and of Co3+ with a closely related tris-aminoethyl amine ligand in combination with XPS data for corresponding surface complexes helped explaining the molecular mechanisms for adsorption and desorption of the LTM cations.
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•Bi- and polyfunctional (P, N)-ferrocene hybrid derivatives.•Catalytic applications of 1,1′- and 1,2-substituted (P, N)-ferrocenes.•Palladium and gold CC cross-coupling ...reactions.•Iridium and iron asymmetric hydrogenation.•Rhodium hydroformylation and silylation.
Unequally functionalized ferrocenes give access to valuable hemilabile reactivity in catalytic reaction. We address the synthesis of hybrid (P, N)-ferrocenyl compounds for which recent catalytic breakthrough applications have been reported, transversely in late transition metals chemistry. Palladium, nickel, rhodium, iridium, and emerging iron and gold catalysis are illustrated from selected examples, which include CC bond formation from cross-coupling and polymerization, allylic substitution, cyanation, hydroformylation, CH arylation and silylation and hydrogenation reactions.
•One-step synthesis of three new carboxylic acid ditertiary phosphines.•Bidentate phosphines bridge two RuII, RhIII or IrIII metal centres.•Internal protonation/P−C(sp3) bond cleavage occurs under ...mild conditions.•Solution and solid-state structures confirmed using NMR and single crystal XRD.
Three new carboxylic acid functionalised diphosphines, R2PCH2N(Ar)CH2PR2 CyL1 R = Cy, Ar = (1-CO2H)(3-OMe)C6H3, CyL2 R = Cy, Ar = (1-CO2H)(3-OH)C6H3 and PhL3 R = Ph, Ar = (1-CO2H)(5-OMe)C6H3 have been prepared from condensation of R2PCH2OH and the appropriate aromatic amine in MeOH, and isolated as colourless solids (for CyL1, CyL2) in good yield. Reaction of CyL1, CyL2, or PhL3, along with the previously reported diphosphines PhL1, PhL2, and PhL4, and RuCl(μ-Cl)(η6-Me2CHC6H4Me)2 in CH2Cl2 affords the P/P-bridging dinuclear ruthenium(II) complexes {RuCl2(η6-Me2CHC6H4Me)}2(μ-CyL1−PhL4) 1a−f as red/orange solids. Careful monitoring by 31P{1H} NMR spectroscopy of CDCl3 solutions of 1a−e revealed remarkably clean P−Csp3 bond cleavage to give RuII mononuclear species 2a−e and the known secondary phosphine complexes RuCl2(η6-Me2CHC6H4Me)(PCy2H) 3 and RuCl2(η6-Me2CHC6H4Me)(PPh2H) 4. Furthermore, facile P−Csp3 bond cleavage of PhL1 can be observed using the chloro-bridged dimers IrCl(μ-Cl)(η5-C5Me5)2 or RhCl(μ-Cl)(η5-C5Me5)2 instead. Deuterium labelling of CyL1, CyL1, PhL1, and PhL2 enabled the assignment of the methylene protons to be confirmed from 1H NMR spectroscopy. All new compounds have been characterised using a range of spectroscopic and analytical techniques. Single crystal X-ray structures have been determined for CyL1, 1d·3OEt2,1f·2CDCl3·OEt2, 2b, 2c, 2d·CDCl3, 2e·0.5OEt2 and 6b·1.5CDCl3. The free phenolic group in CyL1, 1d·3OEt2,1f·2CDCl3·OEt2, 2b and 2d·CDCl3 participates in intra- or intermolecular O−H···O hydrogen bonding.
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► Recent data on the active sites of single-site polymerization catalysts are discussed. ► New insights in the origin of living polymerization on o-fluorinated catalysts are summarized. ► Isolation ...of Cr self-activating ethylene trimerization catalysts gives the key to the mechanism. ► Different active species conduct selective trimerization and tetramerization of ethylene.
Homogeneous single-site alkene polymerization is a “mature” field. However, this does not imply that interest to this research area fades. Moreover, armed by well understood fundamentals of single-site polymerization, researchers get more and more detailed mechanistic data, important for the improvement of the existing catalyst systems, and rational design of new effective catalysts.
This review aims at summarizing the new results obtained over the last few years in unraveling the mechanisms of coordination polymerization of α-olefins and selective oligomerization of ethylene. It is mainly focused on isospecific polymerization, living polymerization, polymerization by late transition metal complexes, and selective trimerization and tetramerization of ethylene.
α-Diimine palladium complexes incorporating phenanthryl- and 6,7-dimethylphenanthrylimino groups have been synthesized and characterized. The (diimine)PdMeCl complexes prepared from 2,3-butanedione ...and acenaphthenequinone bearing the unsubstituted phenanthrylimino groups, 12a and 14a, respectively, exist as a mixtures of syn and anti isomers in a ca. 1:1 ratio. Separation and X-ray diffraction analysis of 14a- syn and 14a- anti isomers confirms the syn/anti assignments. The barrier to interconversion of 14a- syn and 14a- anti via ligand rotation, ΔG ⧧, was found to be 25.5 kcal/mol. The corresponding (diimine)PdMeCl complex prepared from acenaphthenequinone and incorporating the 6,7-dimethylphenanthrylimino group exists solely as the anti isomer, 14b, due to steric crowding which destabilizes the syn isomer. Analogous (diimine)NiBr2 complexes were prepared from 2,3-butanedione incorporating the phenanthrylimino group, 16a, and the 6,7-dimethylphenanthrylimino group, 16b. Nickel-catalyzed polymerizations of ethylene were carried out by activation of the dibromide complexes 16a,b using various aluminum alkyl activators. Complex 16a yields a bimodal distribution polymer, the low-molecular-weight fraction originating from the syn isomer and the high-molecular-weight fraction arising from the anti isomer. Polymerizations carried out by 16b yield only high-molecular-weight polymers with monomodal distributions due to the existence of a single isomer (anti) as the active catalyst. All polymers are linear or nearly so. All catalysts are highly active, but catalysts derived from 16b are somewhat more active than 16a and exhibit turnover frequencies generally over 106 and up to 5 × 106 per hour (40 °C, 27.2 atm ethylene, 15 min). Active palladium ethylene oligomerization catalysts were generated by conversion of the neutral methyl chloride complexes 14a,b to the cationic nitrile complexes 15a,b via halide abstraction.
The one‐step synthesis (33 % isolated yield) of a novel bicyclic diphosphane, P(CH2)2NC6H4(4‐NMe2)2, P−P(NMe2), from the reaction of P(CH2OH)4Cl and H2NC6H4(4‐NMe2) in methanol is described. ...Surprisingly, P−P(NMe2) displays excellent air/solution stability (towards H2O, CH3OH) and can also function efficiently as a bridging ligand. Hence reaction of P−P(NMe2) with Pd(μ−Cl)(η3‐allyl)2 (η3‐allyl=C3H5, C4H7) or Pd(μ−Cl)(κ2−C9H12N)2 affords the singly‐bridged complexes {Pd(Cl)(η3‐allyl)}2{μ‐P−P(NMe2)} 1 a/1 b and {Pd(Cl)(κ2−C9H12N)}2{μ‐P−P(NMe2)} 1 c whereas treatment with MX2(η4‐cod) (M=Pd, Pt; X=Cl, Br, I, Me; η4‐cod=cycloocta‐1,5‐diene) gave (MX2)2{μ‐P−P(NMe2)}2 2 a–e in high yields. Protonation of 2 a–d with HBF4 ⋅ OEt2 gave the corresponding dimethylammonium salts 3 a–d. Single crystal X‐ray studies have been undertaken on P−P(NMe2), 1 b, 2 a, 2 b ⋅ 2CDCl3, 2 d, 2 e, 3 a ⋅ 12CD3CN and 3 b ⋅ 12CD3CN. The P−P bond lengths in free/coordinated P−P(NMe2) remain similar across all compounds studied here and no M ⋅⋅⋅ M contacts were observed within the planar M2P4 ring. In 3 a/3 b the BF4− anion displays a unique secondary interaction with the inorganic six‐membered M2P4 core.
A one‐step synthesis of an air stable, bicyclic dimethylamino‐functionalised diphosphane, P−P(NMe2), is described. Diphosphane P−P(NMe2) shows excellent bridging capabilities towards PdII and PtII affording planar M2P4 6‐membered inorganic rings as inferred by solution and solid state studies. The basic −NMe2 groups undergo facile protonation with acid.
This review provides an outline of the most noteworthy achievements in the area of C-N, C-O and C-P bond formation by hydroamination, hydroalkoxylation, hydrophosphination, hydrophosphonylation or ...hydrophosphinylation reaction on unactivated alkenes (including 1,2- and 1,3-dienes) promoted by first-row late transition metal catalytic systems based on manganese, iron, cobalt, nickel, copper and zinc. The relevant literature from 2009 until mid-2017 has been covered.
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