Bio-Inspired Oxidation Chemistry of a Cu(II)-Fluoride Cryptate with C3-Symmetry

Three copper complexes with an N-methylated cryptand, LTEA, bearing a tris(2-aminoethylamine moiety have been synthesized and compared. Two copper(II)-chloride complexes, [LTEACuCl](SbF6)(MeOH) and [LTEACuCl2](MeCN) were characterized in solution and solid state by UV/Vis and X-ray crystallography. Both had square-based geometries with C1-symmetry and no encapsulation of the chloride ion. A Cu(II)-fluoride complex, in which the ligand is protonated, [LTEAHCuF](BF4)2(MeCN)0.5, adopted C3-symmetry with complete encapsulation of the coordination sphere as characterized by UV/Vis, EPR and X-ray crystallography. Reactivity of the complexes with H2O2/Et3N was explored using UV/Vis and CSI-MS. Only the fluoride complex was found to form a Cu(II)-hydroperoxo intermediate

Self-assembly and magnetic properties of a double-propeller octanuclear copper(II) complex with a meso-helicate-type metallacryptand core

An octanuclear copper(II) complex possessing a dimer-of-tetramers structure self-assembles from a binuclear oxamatocopper(II) metallacryptand of the meso-helicate type; its magnetic behaviour is consistent with its unique double-propeller molecular topology.Pardo Marín, Emilio José, [email protected] ; Julve Olcina, Miguel, [email protected] ; Lloret Pastor, Francisco, [email protected] ; Ruiz Garcia, Rafael, [email protected]

Three-Coordinate Terminal Imidoiron(III) Complexes: Structure, Spectroscopy, and Mechanism of Formation

Article discussing three-coordinate terminal imidoiron(III) complexes and the structure, spectroscopy, and the mechanism of formation

Coupleurs ferromagnétiques (aspects géométrique, topologique et électrochimique)

Ce travail porte sur la synthèse et l'étude de complexes pouvant se connecter à d'autres complexes pour former des entités polynucléaires. Deux tactiques visant à assurer un couplage ferromagnétique au sein du complexe initial dinucléaire (synthon) sont developpées. La première partie est dédiée à des approches statiques : on ne peut influer sur aucun facteur après formation de la molécule. Un premier ligand disposant les deux orbitales magnétiques quasi perpendiculairement conduit à un couplage ferromagnétique faible. Avec ce synthon, des complexes hexanucléaires ont été formés. Ensuite, l'aspect topologique du couplage est inspecté via un mécanisme basé sur la polarisation de spin. La nature du couplage dépend de la disposition des ions métalliques en méta ou para de cycles benzéniques. Les couplages sont importants en dépit de grandes distances entre les ions. A partir des synthons de topologie méta, des complexes polynucléaires à 6, 9 et 16 ions cuivre(II) ont été synthétisés, qui conservent le couplage ferromagnétique de cœur...This work concerns the synthesis and the study of dinuclear complexes capable of anchoring other complexes at their periphery to form polynuclear compounds. Two pathways towards the target to input of a ferromagnetic coupling in the initial complexes have been developed. The first part is dedicated to the static approach where the properties of the complexes cannot be tuned after synthesis. 1) A dinucleating ligand whereby the two magnetic orbitals are orientated in a quasiperpendicular fashion leads to a feeble ferromagnetic coupling. With this synthon hexanuclear complexes were obtained. 2) The topological aspect of the interaction is inspected through a mecanism based on spin polarisation. Biscopper(II) complexes in meta or para positions of benzenic rings lead to differently coupled systemes. The ions are highly coupled despite the large separation between them. Polynuclear compounds containing 6, 9 and 16 Cu(II) ions have been isolated from the meta substituted derivatives and they all retain the ferromagnetic coupling...ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Resonant Acoustic Mixing (RAM) for Efficient Mechanoredox Catalysis without Grinding or Impact Media

Resonant acoustic mixing (RAM) enables mechanoredox catalysis with BaTiO3 as the piezoelectric catalyst on model diazonium coupling reactions. RAM proceeds without formal grinding or impact media, is faster than the analogous ball-milling strategy, and is readily scalable to gram-scale. Combined X-ray diffraction and spectroscopy indicate that reusability of BaTiO3 as a mechanoredox catalyst might be limited by unwanted boration

Propylene polymerization with cyclopentadienyltitanium(IV) hydroxylaminato complexes

Complexes of the type Cp*TiX2(ONR′R′′) (Cp* = η5-C5Me5; X = Me, Cl; R = R′ = Et, TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl); X = R′ = Me, R′′ = tBu) were synthesized by several routes. Upon activation with [Ph3C]+[B(C6F5)4]− and AliBu3, these complexes generate highly active catalysts for propylene polymerization, although significant catalyst deactivation was observed. Activation with B(C6F5)3/AliBu3 or methylaluminoxane (MAO) resulted in reduced polymerization activity, the latter leading to increased catalyst lifetime. Model studies showed that the interaction of AlMe3 with Cp*Ti(Me)2(ONEt2) led to the formation of Cp*Ti(Me)2(η2-O(AlMe3)NEt2). The X-ray crystal structure confirmed that the hydroxylaminato ligand remained η2 bound to the titanium center with the AlMe3 bound to the complex through the oxygen atom of the hydroxylaminato ligand. Exchange reactions with organic ethers revealed the metalloether to be a comparable donor to PhOMe. Cp*Ti(Me)2(ONtBu(Me)) was revealed to be a weaker donor than Cp*Ti(Me)2(ONEt2); Cp*Ti(Me)2(TEMPO) did not bind to AlMe3. AliBu3 bound more weakly to Cp*Ti(Me)2(ONEt2) than AlMe3. Reaction of Cp*Ti(Me)2(ONEt2) and Cp*Ti(Me)2(ONtBu(Me)) with B(C6F5)3 resulted in clean formation of the zwitterionic contact ion pairs [Cp*Ti(Me)(η2-ONEt2)]+[MeB(C6F5)3]− and [Cp*Ti(Me)(η2-ONtBu(Me))]+[MeB(C6F5)3]−, respectively, whereas reaction of Cp*Ti(Me)2(η2-ONtBu(Me)) with [Ph3C]+[B(C6F5)4]− resulted in the clean formation of the solvent-separated ion pair [Cp*Ti(Me)(η2-ONtBu(Me))]+[B(C6F5)4]−. Reaction of Cp*Ti(Me)2(η1-TEMPO) with B(C6F5)3 results in the elimination of methane to result in the formation of the contact ion paired [Cp*Ti(η2-TEMPO)]+[MeB(C6F5)3]−, in which one of the TEMPO methyl groups has undergone C−H activation, resulting in a η2-bound TEMPO ligand, confirmed by 1H, gROESY, and 1H−15N HMBC NMR. Addition of AliBu3 or AlMe3 to the cationic [Cp*Ti(Me)(ONtBu(Me))]+[B(C6F5)4]− resulted in decomposition of the cations

Tuning Inner-Sphere Electron Transfer in a Series of Copper/Nitrosoarene Adducts

International audienceA series of copper/nitrosoarene complexes was created that mimics several steps in biomimetic O2 activation by copper(I). The reaction of the copper(I) complex of N,N,N′,N′-tetramethypropylenediamine with a series of para-substituted nitrosobenzene derivatives leads to adducts in which the nitrosoarene (ArNO) is reduced by zero, one, or two electrons, akin to the isovalent species dioxygen, superoxide, and peroxide, respectively. The geometric and electronic structures of these adducts were characterized by means of X-ray diffraction, vibrational analysis, ultraviolet–visible spectroscopy, NMR, electrochemistry, and density functional theory (DFT) calculations. The bonding mode of the NO moiety depends on the oxidation state of the ArNO moiety: κN for ArNO, mononuclear η2-NO and dinuclear μ-η2:η1 for ArNO•–, and dinuclear μ-η2:η2 for ArNO2–. 15N isotopic labeling confirms the reduction state by measuring the NO stretching frequency (1392 cm–1 for κN-ArNO, 1226 cm–1 for η2-ArNO•–, 1133 cm–1 for dinuclear μ-η2:η1-ArNO•–, and 875 cm–1 for dinuclear μ-η2:η2 for ArNO2–). The 15N NMR signal disappears for the ArNO•– species, establishing a unique diagnostic for the radical state. Electrochemical studies indicate reduction waves that are consistent with one-electron reduction of the adducts and are compared with studies performed on Cu-O2 analogues. DFT calculations were undertaken to confirm our experimental findings, notably to establish the nature of the charge-transfer transitions responsible for the intense green color of the complexes. In fine, this family of complexes is unique in that it walks through three redox states of the ArNO moiety while keeping the metal and its supporting ligand the same. This work provides snapshots of the reactivity of the toxic nitrosoarene molecules with the biologically relevant Cu(I) ion

Mechanochemical Synthesis of Boroxine-linked Covalent Organic Frameworks

We report a rapid, room-temperature mechanochemical synthesis of 2- and 3-dimensional boroxine covalent organic frameworks (COFs), enabled by using trimethylboroxine as a dehydrating additive to overcome the hydrolytic sensitivity of boroxine-based COFs. The resulting COFs display high porosity and crystallinity, with COF-102 being the first example of a mechanochemically-prepared 3D COF, exhibiting a surface area exceeding 2,400 m2 g–1. Mechanochemistry enabled a >20-fold reduction in solvent use and ~100-fold reduction in reaction time compared with solvothermal methods, providing target COFs quantitatively with no additional work-up besides vacuum drying. Real-time Raman spectroscopy permitted the first quantitative kinetic analysis of COF mechanosynthesis, while transferring the reaction design to Resonant Acoustic Mixing (RAM) enabled synthesis of multi-gram amounts of the target COFs