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The reactivity of the monoanionic amidinate ligand [(CH3)3CNC(Ph)NSiMe2NC(Ph)-NHC(CH3)3]Li (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)3]ThCl2 (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)3]UCl3 (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. [ABSTRACT FROM AUTHOR]

A seriesof asymmetric formamidine ligands bearing different substituents withvarious 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 theseasymmetric ligands and their solid-state structures and their behaviorin solution were determined. These complexes were activated with MAO(methylalumoxane) or a combination of cocatalysts and tested in thepolymerization of ethylene and propylene. A noticeable influence ofthe formamidine nitrogen substituents on the activity of the catalystand properties of the obtained polymers was observed. Further, a plausiblemechanism for the polymerization of propylene is presented derivedfrom a combination of ESR-C60and MALDI-TOF trapping experimentswhich shed light on the nature of the active catalytic species. [ABSTRACT FROM AUTHOR]

A series of titanium bis(amidinate)complexes containing pendantarms as one of the amidinate N substituents have been prepared andstudied in the polymerization of propylene after their activationwith MAO and other cocatalysts. The type of pendant arm greatly influencesthe reactivity and stereospecificity of the resulting polymers. Theeffect of the cocatalyst nature, its amount, and the time of the reactionhave a dramatic effect on the reactivity of a titanium bis(amidinate)bis(dimethylamido) precatalyst containing a furyl group at the pendantarm. [ABSTRACT FROM AUTHOR]

The steric properties of variousnitrogen substituents on amidineswere tuned in order to obtain group 4 mono- and bis(amidinate) dimethylamidoor chloride complexes. The amidinate dimethylamido and chloride complexeswere prepared, and their solid-state as well as their solution-statestructures were studied. After the activation by MAO, these complexeswere tested in the polymerization of propylene and ethylene. A noticeableinfluence of the amidine carbon and nitrogen substituents on the activityof the catalyst and properties of the obtained polymer was observed.Further, a plausible mechanism for the ethylene polymerization processis presented taking into account a combination of ESR-C60and MALDI-TOF experiments, shedding light on the nature of the catalyticspecies. [ABSTRACT FROM AUTHOR]

Bis(amidinate) titanium and zirconium bis(dimethylamido)complexeswere prepared, and the dynamic behavior of the titanium complex containingperfluorinated amidinate ligand (11) was studied in detail.The variable-temperature NMR revealed the presence of two speciesin solution, in line with the different connection modes of the ligandto the metal center. The resulting complexes were tested as catalystsin the polymerization of propylene, and the resulting polymers wereconsistent with elastomeric high-molecular-weight atactic polypropylenes. [ABSTRACT FROM AUTHOR]

Polystyrene-b-polyethylene glycol (PS-b-PEG) amphiphilic block copolymers featuring a terminal tridentate N,N,N-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 Mn2+, Fe2+, Ni2+, and Zn2+, the resulting metallo-polymers were self-assembled into spherical, vesicular nanostructures, as characterized by dynamic light scattering and transmission electron microscopy (TEM) imaging. [ABSTRACT FROM AUTHOR]

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 (UO22+) ion and characterized via single-crystal X-ray diffraction. 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]