Zirconium-mediated carbon-fluorine bond functionalisation through cyclohexyne "umpolung".

Polarity reversal, or "umpolung", is a widely acknowledged strategy to allow organic functional groups amenable to react in alternative ways to the usual preference set by their electronic features. In this article, we demonstrate that cyclohexyne umpolung, realized through complexation to zirconocene, makes the small strained cycloalkyne amenable to C-F bond functionalisation. Such strong bond activation chemistry is unprecedented in "free" aryne and strained alkyne chemistry.

Synthesis and characterization of heptacoordinated molybdenum(II) complexes supported with 2,6-bis(pyrazol-3-yl)pyridine (bpp) ligands.

Functional pincer ligands that engage in metal-ligand cooperativity and/or are capable of redox non-innocence have found a great deal of success in catalysis. These two properties may be found in metal complexes of the 2,6-bis(pyrazol-3-yl)pyridine (bpp) ligands. With this goal in mind, we have attempted the coordination of 2,6-bis(5-trifluoromethylpyrazol-3-yl)pyridine (LCF3) and its Bu analogue 2,6-bis(5--butylpyrazol-3-yl)pyridine (LtBu) to Mo(0) by reactions with mixed phosphine/carbonyl complexes [Mo(CO)(MeCN)(PMePh)] 1-3 (1 ≤ ≤ 3).

F-Naf PET/CT in pseudarthrosis after anterior cervical discectomy and fusion.

Background Context: Pseudarthrosis is a well-known cause of persistent or recurrent pain after anterior cervical discectomy and fusion (ACDF). Numerous radiographic criteria to determine the fusion status has been described in the literature, but their accuracies in clinical practice vary considerably and no 1 single method has proved superior. Fluorine-18 sodium fluoride (F-NaF) positron emission tomography/computed tomography (PET/CT), depicting osteoblastic activity, might be useful to identify pseudarthrosis after ACDF.

Reactivity of metal hydrides with CO: going beyond formate with a high-valent cationic pentahydride Mo(vi) complex.

The cationic molybdenum pentahydride complex [MoH(depe)] (depe = 1,2-bis(diethylphosphino)ethane) is shown to undergo two consecutive reactions with carbon dioxide. In the initial, room-temperature process, classical insertion of CO into a metal-hydride bond is observed, resulting in the formation of the expected formate complex, [MoH(HCOO)(depe)]. Further reactivity is triggered at temperature above 100 °C.

Low-valent group 6 metals/Al(CF) donor-acceptor systems for CO activation and cleavage.

Donor-acceptor systems for CO activation combining a formally zero-valent group 6 metal as the donor with the Lewis acid Al(CF) (AlCF) are reported. They were obtained from AlCF adducts of N-complexes by N-to-CO substitution. One species was capable of C-O cleavage.

Coordination of Al(CF) B(CF) on group 6 end-on dinitrogen complexes: chemical and structural divergences.

The coordination of the Lewis superacid tris(pentafluorophenyl)alane (AlCF) to phosphine-supported, group 6 bis(dinitrogen) complexes [ML(N)] is explored, with M = Cr, Mo or W and L = dppe (1,2-bis(diphenylphosphino)ethane), depe (1,2-bis(diethylphosphino)ethane), dmpe (1,2-bis(dimethylphosphino)ethane) or 2 × PMePh. Akin to tris(pentafluorophenyl)borane (BCF), AlCF can form 1 : 1 adducts by coordination to one distal nitrogen of general formula -[ML(N){(μ-η:η-N)Al(CF)}]. The boron and aluminium adducts are structurally similar, showing a comparable level of N push-pull activation.

Seven-Coordinate Group 6 Metal Hydrides Obtained by H Activation at B(CF) Adducts of N Complexes: Frustrated Lewis Pair-Type Reactivity of The B-N Linkage.

The adducts 2 of general formula trans-[(L)M{RP(CH)PR}{NB(CF)}] (L=ø or N, M=Mo or W, R=Et or Ph), formed from Lewis acid-base pairing of B(CF) to a dinitrogen ligand of zero-valent group 6 bis(phosphine) complexes trans-[M{RP(CH)PR}(N)] are shown to react with dihydrogen to afford hepta-coordinated bis(hydride) complexes [M(H){RP(CH)PR}{NB(CF)}] 3 which feature the rare ability to activate both dinitrogen and dihydrogen at a single metal center, except in the case where M=Mo and R=Ph for which fast precipitation of insoluble [Mo(H)(dppe)] (dppe=1,2-bis(diphenylphosphino)ethane) occurs. The frustrated Lewis pair (FLP)-related reactivity of the B-N linkage in compounds 3 was explored and led to distal N functionalization without involvement of the hydride ligands. It is shown in one example that the resulting bis(hydride) diazenido compounds may also be obtained through a sequence involving first FLP-type N-functionalization followed by oxidative addition of H.

Nitrogen Fixation by Manganese Complexes - Waiting for the Rush?

Manganese is currently experiencing a great deal of attention in homogeneous catalysis as a sustainable alternative to platinum group metals due to its abundance, affordable price and low toxicity. While homogeneous nitrogen fixation employing well-defined transition metal complexes has been an important part of coordination chemistry, manganese derivatives have been only sporadically used in this research area. In this contribution, the authors systematically cover manganese organometallic chemistry related to N activation spanning almost 60 years, identify apparent pitfalls and outline encouraging perspectives for its future development.

Value of F-FDG PET/CT to Identify Occult Infection in Presumed Aseptic Pseudarthrosis after Spinal Fusion: Correlation with Intraoperative Cultures.

 Fluorine-18 fluorodeoxyglucose ( F-FDG) positron emission tomography/computed tomography (PET/CT) has gained attention as an emerging tool in case of suspicion of infection on spine, whether native or instrumented. However, the diagnostic performance of F-FDG PET/CT in clinically occult low-grade surgical site infection (SSI) after spinal fusion, an important risk factor for pseudarthrosis, remains unknown.  We retrospectively identified all the presumed aseptic patients with pseudarthrosis confirmed by revision surgery who underwent preoperative F-FDG PET/CT scans performed between April 2019 and November 2022.

Metallomimetic C-F Activation Catalysis by Simple Phosphines.

Delivering metallomimetic reactivity from simple p-block compounds is highly desirable in the search to replace expensive, scarce precious metals by cheap and abundant elements in catalysis. This contribution demonstrates that metallomimetic catalysis, involving facile redox cycling between the P(III) and P(V) oxidation states, is possible using only simple, cheap, and readily available trialkylphosphines without the need to enforce unusual geometries at phosphorus or use external oxidizing/reducing agents. Hydrodefluorination and aminodefluorination of a range of fluoroarenes was realized with good to very good yields under mild conditions.

Biomimetic catalysis of nitrite reductase enzyme using copper complexes in chemical and electrochemical reduction of nitrite.

Copper nitrite reductase mimetics were synthesized using three new tridentate ligands sharing the same ,, motif of coordination. The ligands were based on L-proline modifications, attaching a pyridine and a triazole to the pyrrolidine ring, and differ by a pendant group (R = phenyl, -butyl and -propan-1-ol). All complexes coordinate nitrite, as evidenced by cyclic voltammetry, UV-Vis, FTIR and electron paramagnetic resonance (EPR) spectroscopies.

An Experimental and Computational Investigation Rules Out Direct Nucleophilic Addition on the N Ligand in Manganese Dinitrogen Complex [Cp(CO) Mn(N )].

We have re-examined the reactivity of the manganese dinitrogen complex [Cp(CO) Mn(N )] (1, Cp=η -cyclopentadienyl, C H ) with phenylithium (PhLi). By combining experiment and density functional theory (DFT), we have found that, unlike previously reported, the direct nucleophilic attack of the carbanion onto coordinated dinitrogen does not occur. Instead, PhLi reacts with one of the CO ligands to provide an anionic acylcarbonyl dinitrogen metallate [Cp(CO)(N )MnCOPh]Li (3) that is stable only below -40 °C.

Assessing Combinations of B(C F ) and N -Derived Molybdenum Nitrido Complexes for Heterolytic Bond Activation.

Two different dinitrogen-derived molybdenum nitrido complexes varying by their geometry, ligand spheres and oxidations states were shown to engage their N ligand in dative bonding with the strong Lewis acid B(C F ) . The stable adducts were assessed for frustrated Lewis pair-type heterolytic E-H bond splitting of hydrosilanes (E=Si) and HB(C F ) . Whereas Si-H bond activation was achieved, HB(C F ) was shown to substitute B(C F ) in a quantitative or equilibrated fashion, depending on the nature of the nitrido complex.

F-NaF PET/CT in Presumed Aseptic Pseudarthrosis after Spinal Fusion: Correlation with Findings at Revision Surgery and Intraoperative Cultures.

 Conventional imaging is useful to assess interbody fusion by showing complete trabecular bony bridging, but has a low positive predictive value for pseudarthrosis. Because alterations of bone metabolism may precede structural anatomical changes on computed tomography (CT), we aimed to investigate the ability of fluorine 18 sodium fluoride positron emission tomography/computed tomography ( F-NaF PET/CT) to identify pseudarthrosis after spinal fusion using surgical revision as the reference standard.  We retrospectively reviewed F-NaF PET/CT scans performed between February 2019 and September 2020 in patients experiencing pain after spinal fusion.

Dinitrogen-derived (diarylboryl)diazenido complexes with differing coordination to the thallium cation.

To prepare N-derived cationic boryldiazenido-tungsten complexes as models of semimetallic metal-borinium frustrated Lewis pairs activating N, we have attempted halide abstraction from -(diarylboryl)diazenido-halo-tungsten complexes. Reactions with Tl led to adducts in which coordination of the cation differs depending on the boryldiazenide substituents and the ancillary ligand. Chloride scavenging was not observed.

Temporal Archive of Atmospheric Microplastic Deposition Presented in Ombrotrophic Peat.

Ombrotrophic peatland-fed solely from atmospheric deposition of nutrients and precipitation-provide unique archives of atmospheric pollution and have been used to illustrate trends and changes in atmospheric trace element composition from the recent decadal to the Holocene period. With the acknowledgment of atmosphere plastic pollution, analysis of ombrotrophic peat presents an opportunity to characterize the historical atmospheric microplastic pollution prevalence. Ombrotrophic peatland is often located in comparatively pristine mountainous and boreal areas, acting as sentinels of environmental change.

Borane-catalysed dinitrogen borylation by 1,3-B-H bond addition.

The borylation of ligated dinitrogen by 1,3-B-H bond addition over a W-N[triple bond, length as m-dash]N unit using various hydroboranes has been examined. In a previous study, we have shown that Piers' borane (1) reacted with the tungsten dinitrogen complex 2 to afford a boryldiazenido-hydrido-tungsten species. The ease and mildness of this reaction have encouraged us to extend its scope, with the working hypothesis that 1 could potentially catalyse the 1,3-B-H bond addition of other hydroboranes.

Spatial distribution of pharmaceuticals within the particulate phases of a peri-urban stream.

Pharmaceutical products (PPs) are consumed worldwide and are continuously released into hydrological environments, but are not efficiently removed by sewage treatment plants. Their occurrence within the dissolved phase has been extensively studied, but only a few articles concern solid matrices. The mechanisms and extent of sorption depend on the properties of both the molecules (degradability, charge, hydrophobicity) and the matrices (clay content, organic matter content), making the spatio-temporal distribution of PPs in natural environments complex and poorly elucidated.

Synthesis, Characterization, and Comparative Theoretical Investigation of Dinitrogen-Bridged Group 6-Gold Heterobimetallic Complexes.

We have prepared and characterized a series of unprecedented group 6-group 11, N-bridged, heterobimetallic [ML(η-N)(μ-η:η-N)Au(NHC)] complexes (M = Mo, W, L = diphosphine) by treatment of -[ML(N)] with a cationic gold(I) complex [Au(NHC)]. The adducts are very labile in solution and in the solid, especially in the case of molybdenum, and decomposition pathways are likely initiated by electron transfers from the zerovalent group 6 atom to gold. Spectroscopic and structural parameters point to the fact that the gold adducts are very similar to Lewis pairs formed out of strong main-group Lewis acids (LA) and low-valent, end-on dinitrogen complexes, with a bent M-N-N-Au motif.

Microsurgical Transcranial Approach of 112 Paraoptic Meningiomas: A Single-Center Case Series.

Background: Predictors of visual outcomes after optic nerve decompression are controversial.

Objective: To identify the predictors of poor visual outcomes after surgery of meningiomas responsible of a compressive optic neuropathy.

Methods: We focused on paraoptic meningiomas (POMs), which gathered tuberculum sellae meningiomas (TSMs) and anterior clinoid meningiomas (ACMs) responsible for visual impairment or threatening visual function, that underwent surgery at our institution between January 2009 and December 2015 and analyzed the clinical and radiological findings of our patients.

New Insights into Expression of Hormonal Receptors by Meningiomas.

Objective: Meningiomas have a female predilection, which is even stronger for spinal than for intracranial meningiomas. The relationship between meningiomas and endogenous or exogenous sex hormones such as cyproterone acetate (CPA) is well documented, yet their underlying mechanism remains unknown. Clarification of the expression profile of hormonal receptors by meningiomas would help us to better understand their hormonal susceptibility.

Frustrated Lewis Pair Chemistry Enables N Borylation by Formal 1,3-Addition of a B-H Bond in the Coordination Sphere of Tungsten.

The first example of a formal 1,3-B-H bond addition across the M-N≡N unit of an end-on dinitrogen complex has been achieved. The use of Piers' borane HB(C F ) was essential to observe this reactivity and it plays a triple role in this transformation: 1) electrophilic N -borylation agent, 2) Lewis acid in a frustrated Lewis pair-type B-H bond activation, and 3) hydride shuttle to the metal center. This chemistry is supported by NMR spectroscopy and solid-state characterization of products and intermediates.