Accurately characterizing actinide oxides bound to metal-organic frameworks (MOFs) is important for designing MOFs as radioactive waste sorbents and catalytic supports. In this work, the zirconium ...MOF NU-1000 was post-synthetically modified through solvothermal deposition to include the uranyl (UO
2
2+
) ion and characterized
via
single-crystal X-ray diffraction. Bond lengths derived from the diffraction pattern and Raman spectroscopy indicate that UO
2
2+
maintains its chemical properties upon deposition, while alcohol oxidation photocatalysis reveals photo-interactions between the pyrene linkers and the UO
2
2+
ion.
The zirconium MOF NU-1000 was post-synthetically modified through solvothermal deposition to include the uranyl ion and characterized
via
single-crystal X-ray diffraction; photo-oxidation was also performed.
The current perspective will present the use of amidinate group 4 complexes in α-olefin polymerizations. We will present the structural studies of the complexes bearing various numbers of amidinates ...as spectator ligands, with a special emphasis on the bis(amidinate) group 4 systems. The mechanistic studies elucidate the influence of various reaction conditions on the behaviour of the reactive species. Additionally, the study of the active species by techniques such as EPR spectroscopy and MALDI-TOF spectrometry are presented. We will also demonstrate how, based on such techniques, highly stereospecific bis(amidinate) titanium complexes may be designed and applied in the polymerization of propylene.
The current perspective will present the use of amidinate group 4 complexes in α-olefin polymerizations.
Polystyrene-
-polyethylene glycol (PS-
-PEG) amphiphilic block copolymers featuring a terminal tridentate
-ligand (terpyridine) were synthesized for the first time through an efficient route. In this ...approach, telechelic chain-end modified polystyrenes were produced via reversible addition-fragmentation chain-transfer (RAFT) polymerization by using terpyridine trithiocarbonate as the chain-transfer agent, after which the hydrophilic polyethylene glycol (PEG) block was incorporated into the hydrophobic polystyrene (PS) block in high yields via a thiol-ene process. Following metal-coordination with Mn
, Fe
, Ni
, and Zn
, the resulting metallo-polymers were self-assembled into spherical, vesicular nanostructures, as characterized by dynamic light scattering and transmission electron microscopy (TEM) imaging.
The interactions between uranium and non‐innocent organic species are an essential component of fundamental uranium redox chemistry. However, they have seldom been explored in the context of ...multidimensional, porous materials. Uranium‐based metal–organic frameworks (MOFs) offer a new angle to study these interactions, as these self‐assembled species stabilize uranium species through immobilization by organic linkers within a crystalline framework, while potentially providing a method for adjusting metal oxidation state through coordination of non‐innocent linkers. We report the synthesis of the MOF NU‐1700, assembled from U4+‐paddlewheel nodes and catecholate‐based linkers. We propose this highly unusual structure, which contains two U4+ ions in a paddlewheel built from four linkers—a first among uranium materials—as a result of extensive characterization via powder X‐ray diffraction (PXRD), sorption, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA), in addition to density functional theory (DFT) calculations.
Through solvothermal combination of uranyl and a redox‐active linker, we reduced the U−O bonds and subsequently formed a metal‐organic framework built from a uranium paddlewheel node. This paddlewheel node, where two uranium atoms are connected by four hexahydroxytriphenylene species and capped with water moieties, is unprecedented.
A series of titanium bis(amidinate) complexes containing pendant arms as one of the amidinate N substituents have been prepared and studied in the polymerization of propylene after their activation ...with MAO and other cocatalysts. The type of pendant arm greatly influences the reactivity and stereospecificity of the resulting polymers. The effect of the cocatalyst nature, its amount, and the time of the reaction have a dramatic effect on the reactivity of a titanium bis(amidinate) bis(dimethylamido) precatalyst containing a furyl group at the pendant arm.
The steric properties of various nitrogen substituents on amidines were tuned in order to obtain group 4 mono- and bis(amidinate) dimethylamido or chloride complexes. The amidinate dimethylamido and ...chloride complexes were prepared, and their solid-state as well as their solution-state structures were studied. After the activation by MAO, these complexes were tested in the polymerization of propylene and ethylene. A noticeable influence of the amidine carbon and nitrogen substituents on the activity of the catalyst and properties of the obtained polymer was observed. Further, a plausible mechanism for the ethylene polymerization process is presented taking into account a combination of ESR-C60 and MALDI-TOF experiments, shedding light on the nature of the catalytic species.
The reactivity of the monoanionic amidinate ligand (CH3)3CNC(Ph)NSiMe2NC(Ph)-NHC(CH3)3Li (1) with a silyl amido side arm towards the early actinides, uranium and thorium, was investigated. While the ...salt metathesis reaction with ThCl4(thf)3 afforded the bis(amidinate)thorium(iv) dichloride complex (CH3)3CNC(Ph)NSi(CH3)2NC(Ph)-NHC(CH3)3ThCl2 (2) in high yield, the reaction of ligand 1 with UCl4 leads to a Lewis acid supported nucleophilic attack of an incoming ligand unit, yielding the trichloro uranium complex (CH3)3CNC(Ph)Si(CH3)2-N(C(CH3)3)C(Ph)NSi(CH3)2NC(Ph)N-(C(CH3)3UCl3 (4). The exposure of in situ formed complex 2 to wet THF solutions (<1% w of water), gave the mono(amidinate)Th(iv)(chloro)(bis-hydroxo) dimeric complex (CH3)3CNC(Ph)NSiMe2NC(Ph)NHC(CH3)3Th(OH)2(Cl)2·(3) as bright red needles, exhibiting extremely short Th-OH bond distances (1.741(5) Å and 1.737(5) Å). The reactivity of the thorium complex 2 in the ring opening polymerization (ROP) was studied, showing high activity. Thermodynamic and kinetic measurements were performed to shed light on the mechanism for the ROP.
Accurately characterizing actinide oxides bound to metal–organic frameworks (MOFs) is important for designing MOFs as radioactive waste sorbents and catalytic supports. Here, the zirconium MOF ...NU-1000 was post-synthetically modified through solvothermal deposition to include the uranyl (UO22+) ion and characterized via single-crystal X-ray diffraction. Additonally, bond lengths derived from the diffraction pattern and Raman spectroscopy indicate that UO22+ maintains its chemical properties upon deposition, while alcohol oxidation photocatalysis reveals photo-interactions between the pyrene linkers and the UO22+ ion.
Bis(amidinate) titanium and zirconium bis(dimethylamido) complexes were prepared, and the dynamic behavior of the titanium complex containing perfluorinated amidinate ligand (11) was studied in ...detail. The variable-temperature NMR revealed the presence of two species in solution, in line with the different connection modes of the ligand to the metal center. The resulting complexes were tested as catalysts in the polymerization of propylene, and the resulting polymers were consistent with elastomeric high-molecular-weight atactic polypropylenes.
A series of asymmetric formamidine ligands bearing different substituents with various steric and electronic properties on the nitrogen of the N–C–N motif were synthesized. Group 4 ...bis(formamidinate) dimethylamido, chloride, and benzyl complexes were studied using these asymmetric ligands and their solid-state structures and their behavior in solution were determined. These complexes were activated with MAO (methylalumoxane) or a combination of cocatalysts and tested in the polymerization of ethylene and propylene. A noticeable influence of the formamidine nitrogen substituents on the activity of the catalyst and properties of the obtained polymers was observed. Further, a plausible mechanism for the polymerization of propylene is presented derived from a combination of ESR-C60 and MALDI-TOF trapping experiments which shed light on the nature of the active catalytic species.
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