Synthesis of Mn(III)X3 (X = Cl, Br, I) Compounds with Phosphine (R3P) Ligands.

This work details the synthesis and characterization of complexes of the form [MnIIIX3(PR3)2] (X = Cl, Br, I), which is a rare type of coordination compound. Prior to this work, the only mode of synthesis was oxidizing mixtures of MnIIX2 and PR3 with dry air, but these procedures give low yields and variable outcomes. By taking advantage of the starting material [MnIIICl3(OPPh3)2] (1) and other new strategies, we present robust synthetic protocols for both new and known Mn(III) halido phosphine complexes. In addition to [MnIIIX3(PR3)2], these include [MnIIICl2(dmpe)2]+ salts and [LMnIIX3]- manganates (L = phosphine oxide). Furthermore, the full characterization of these [MnIIIX3(PR3)2] species enabled a definitive revisitation of some controversial chemistry surrounding the compounds and products from the dry air oxidation of certain MnIIX2 and phosphine ligand mixtures.

Manganese(III) Nitrate Complexes as Bench-Stable Powerful Oxidants.

We report herein a convenient one-pot synthesis for the shelf-stable molecular complex [Mn(NO3)3(OPPh3)2] (2) and describe the properties that make it a powerful and selective one-electron oxidation (deelectronation) reagent. 2 has a high reduction potential of 1.02 V versus ferrocene (MeCN) (1.65 vs normal hydrogen electrode), which is one the highest known among readily available redox agents used in chemical synthesis. 2 exhibits stability toward air in the solid state, can be handled with relative ease, and is soluble in most common laboratory solvents such as MeCN, dichloromethane, and fluorobenzene. 2 is substitutionally labile with respect to the coordinated (pseudo)halide ions enabling the synthesis of other new Mn(III) nitrato complexes also with high reduction potentials ranging from 0.6 to 1.0 V versus ferrocene.

Experimental and Computational Determination of a M-Cl Homolytic Bond Dissociation Free Energy: Mn(III)Cl-Mediated C-H Cleavage and Chlorination.

This study confirms the hypothesis that [MnCl3(OPPh3)2] (1) and acetonitrile-solvated MnCl3 (i.e., [MnCl3(MeCN)x]) can be used as synthons to prepare Mn(III) chloride complexes with facially coordinating ligands. This was achieved through the preparation and characterization of six new {MnIIICl} complexes using anionic ligands TpH (tris(pyrazolyl)borate) and TpMe (tris(3,5-dimethylpyrazolyl)borate). The MnIII-chloride dissociation and association equilibria (Keq) and MnIII/II reduction potentials were quantified in DCM. These two thermochemical parameters (Keq and E1/2), in addition to the known Cl-atom reduction potential in DCM, enabled the quantification of the Mn-Cl bond dissociation (homolysis) free energy of 21 and 23 ± 7 kcal/mol at room temperature for R = H and Me, respectively. These are in reasonable agreement with the bond dissociation free energy (BDFEM-Cl) of 34 ± 6 kcal/mol calculated using density functional theory. The BDFEM-Cl of 1 was also calculated (25 ± 6 kcal/mol). These energies were used in predictive C-H bond reactivity.

Dinuclear Mn(I) Complexes with Phosphido and Hydrido Bridges: Synthesis, Reactivity, and Hydrogenative Catalysis.

A class of organomanganese hydrogenation catalysts was recently rediscovered. These are simple dinuclear Mn(I) carbonyl compounds with phosphido (PR2 - ) and hydrido (H- ) bridges. This class of compounds has been known since the 1960's, and they have rich coordination chemistry and reactivity. Given their recently discovered potential for catalytic applications, a fresh look at this class of compounds was necessary. Hence, this Review comprehensively covers the synthesis, reactivity, and catalysis of this interesting class of molecules.

Synthesis of a Bench-Stable Manganese(III) Chloride Compound: Coordination Chemistry and Alkene Dichlorination.

The complex [MnCl3(OPPh3)2] (1) is a bench-stable and easily prepared source of MnCl3. It is prepared by treating acetonitrile solvated MnCl3 (2) with Ph3PO and collecting the resulting blue precipitate. 1 is useful in coordination reactions by virtue of the labile Ph3PO ligands, and this is demonstrated through the synthesis of {Tpm*}MnCl3 (3). In addition, methodologies in synthesis that rely on difficult or cumbersome to prepare solutions of reactive MnCl3 can be accomplished using 1 instead. This is demonstrated through alkene dichlorinations in a wide range of solvents, open to air, and with good substrate scope. Light-accelerated halogenation and radical sensitive experiments support a radical mechanism involving stepwise Cl-atom transfer(s) from 1.

Bench-Stable Dinuclear Mn(I) Catalysts in E-Selective Alkyne Semihydrogenation: A Mechanistic Investigation.

Dinuclear manganese hydride complexes of the form [Mn2 (CO)8 (µ-H)(µ-PR2 )] (R=Ph, 1; R=iPr, 2) were used in E-selective alkyne semi-hydrogenation (E-SASH) catalysis. Catalyst speciation studies revealed rich coordination chemistry and the complexes thus formed were isolated and in turn tested as catalysts; the results underscore the importance of dinuclearity in engendering the observed E-selectivity and provide insights into the nature of the active catalyst. The insertion product obtained from treating 2 with (cyclopropylethynyl)benzene contains a cis-alkenyl bridging ligand with the cyclopropyl ring being intact. Treatment of this complex with H2 affords exclusively trans-(2-cyclopropylvinyl)benzene. These results, in addition to other control experiments, indicate a non-radical mechanism for E-SASH, which is highly unusual for Mn-H catalysts. The catalytically active species are virtually inactive towards cis to trans alkene isomerization indicating that the E-selective process is intrinsic and dinuclear complexes play a critical role. A reaction mechanism is proposed accounting for the observed reactivity which is fully consistent with a kinetic analysis of the rate limiting step and is further supported by DFT computations.

Hydrogenative Catalysis with Three-Coordinate Zinc Complexes Supported with PN Ligands is Enhanced Compared to PNP Analogs.

This work details the synthesis, characterization, and catalytic activity of reactive low-coordinate organozinc complexes. The complexes activate hydrogen and they appear to be more active in hydrogenation of ketones and imines than their tridentate pincer analogs. This is thought, in part, to be due to the lack of trailing third phosphorus arm present in previous work. DFT computations reveal a sigma-bond metathesis mechanism is comparable to an alternative aromatization/dearomatization metal-ligand cooperative mechanism.

Which outcomes should be used in future bronchiolitis trials? Developing a bronchiolitis core outcome set using a systematic review, Delphi survey and a consensus workshop.

OBJECTIVES: The objective of this study was to develop a core outcome set (COS) for use in future clinical trials in bronchiolitis. We wanted to find out which outcomes are important to healthcare professionals (HCPs) and to parents and which outcomes should be prioritised for use in future clinical trials. DESIGN AND SETTING: The study used a systematic review, workshops and interviews, a Delphi survey and a final consensus workshop. RESULTS: Thirteen parents and 45 HCPs took part in 5 workshops; 15 other parents were also separately interviewed. Fifty-six items were identified from the systematic review, workshops and interviews. Rounds one and two of the Delphi survey involved 299 and 194 participants, respectively. Sixteen outcomes met the criteria for inclusion within the COS. The consensus meeting was attended by 10 participants, with representation from all three stakeholder groups. Nine outcomes were added, totalling 25 outcomes to be included in the COS. CONCLUSION: We have developed the first parent and HCP consensus on a COS for bronchiolitis in a hospital setting. The use of this COS will ensure outcomes in future bronchiolitis trials are important and relevant, and will enable the trial results to be compared and combined. TRIAL REGISTRATION NUMBER: ISRCTN75766048.

Development, implementation and evaluation of an evidence-based paediatric early warning system improvement programme: the PUMA mixed methods study.

BACKGROUND: Paediatric mortality rates in the United Kingdom are amongst the highest in Europe. Clinically missed deterioration is a contributory factor. Evidence to support any single intervention to address this problem is limited, but a cumulative body of research highlights the need for a systems approach. METHODS: An evidence-based, theoretically informed, paediatric early warning system improvement programme (PUMA Programme) was developed and implemented in two general hospitals (no onsite Paediatric Intensive Care Unit) and two tertiary hospitals (with onsite Paediatric Intensive Care Unit) in the United Kingdom. Designed to harness local expertise to implement contextually appropriate improvement initiatives, the PUMA Programme includes a propositional model of a paediatric early warning system, system assessment tools, guidance to support improvement initiatives and structured facilitation and support. Each hospital was evaluated using interrupted time series and qualitative case studies. The primary quantitative outcome was a composite metric (adverse events), representing the number of children monthly that experienced one of the following: mortality, cardiac arrest, respiratory arrest, unplanned admission to Paediatric Intensive Care Unit, or unplanned admission to Higher Dependency Unit. System changes were assessed qualitatively through observations of clinical practice and interviews with staff and parents. A qualitative evaluation of implementation processes was undertaken. RESULTS: All sites assessed their paediatric early warning systems and identified areas for improvement. All made contextually appropriate system changes, despite implementation challenges. There was a decline in the adverse event rate trend in three sites; in one site where system wide changes were organisationally supported, the decline was significant (ß = -0.09 (95% CI: - 0.15, - 0.05); p = < 0.001). Changes in trends coincided with implementation of site-specific changes. CONCLUSIONS: System level change to improve paediatric early warning systems can bring about positive impacts on clinical outcomes, but in paediatric practice, where the patient population is smaller and clinical outcomes event rates are low, alternative outcome measures are required to support research and quality improvement beyond large specialist centres, and methodological work on rare events is indicated. With investment in the development of alternative outcome measures and methodologies, programmes like PUMA could improve mortality and morbidity in paediatrics and other patient populations.

National survey of feasibility of NIV trials for management of children with bronchiolitis.

BACKGROUND: Bronchiolitis is a major cause of admission to hospital in children. Non-invasive ventilation (NIV) support with continuous positive airway pressure (CPAP) or high-flow nasal cannula (HFNC) oxygen is routinely used for infants in the UK with bronchiolitis. OBJECTIVE: To establish UK paediatric practice regarding management of bronchiolitis, and to explore issues pertinent to the design of a potential future randomised controlled trial of NIV. DESIGN: Screening logs were completed in hospitals in England capturing information on paediatric bronchiolitis admissions. An online national survey of clinical practice was disseminated to healthcare professionals (HCPs) across the UK to ascertain current management strategies. RESULTS: Screening logs captured data on 393 infants from 8 hospitals. Reasons for admission were most commonly respiratory distress and/or poor fluid intake. Oxygen was administered for 54% of admissions. Respiratory (CPAP and HFNC) and non-respiratory support administered varied considerably. The national survey was completed by 111 HCPs from 76 hospitals. Data were obtained on criteria used to commence and wean NIV, responsibilities for altering NIV settings, minimum training requirements for staff managing a child on NIV, and numbers of trained staff. Most centres were interested in and capable of running a trial of NIV, even out of normal office hours. CONCLUSIONS: Respiratory and non-respiratory management of bronchiolitis in UK centres varies widely. A trial of HFNC oxygen therapy in this group of patients is feasible and HCPs would be willing to randomise patients into such a trial. Future work should focus on defining trial eligibility criteria.

A hemilabile manganese(I)-phenol complex and its coordination induced O-H bond weakening.

The known compound K[(PO)2Mn(CO)2] (PO = 2-((diphenylphosphino)methyl)-4,6-dimethylphenolate) (K[1]) was protonated to form the new Mn(i) complex (HPO)(PO)Mn(CO)2 (H1) and was determined to have a pKa approximately equal to tetramethylguanidine (TMG). The reduction potential of K[1] was determined to be -0.58 V vs. Fc/Fc+ in MeCN and allowed for an estimation of an experimental O-H bond dissociation free energy (BDFEO-H) of 73 kcal mol-1 according to the Bordwell equation. This value is in good agreement with a corrected DFT computed BDFEO-H of 68.0 kcal mol-1 (70.3 kcal mol-1 for intramolecular H-bonded isomer). The coordination of the protonated O-atom in the solid-state H1 was confirmed using FTIR spectroscopy and X-ray crystallography. The phenol moiety is hemilabile as evident from computation and experimental results. For instance, dissociation of the protonated O-atom in H1 is endergonic by only a few kcal mol-1 (DFT). Furthermore, [1]- and other Mn(i) compounds coordinated to PO and/or HPO do not react with MeCN, but H1 reacts with MeCN to form H1+MeCN. Experimental evidence for the solution-bound O-atoms of H1 was obtained from 1H NMR and UV-vis spectroscopy and by comparing the electronic spectra of bona fide 16-e- Mn(i) complexes such as [{PNP}Mn(CO)2] (PNP = -N{CH2CH2(PiPr2)}2) and [(Me3SiOP)(PO)Mn(CO)2] (Me3Si1). Compound H1 is only meta-stable (t1/2 0.5-1 day) and decomposes into products consistent with homolytic O-H bond cleavage. For instance, treatment of H1 with TEMPO resulted in formation of TEMPOH, free ligand, and [MnII{(PO)2Mn(CO)2}2]. Together with the experimental and calculated weakened BDFEO-H, these data provide strong evidence for the coordination and hemilability of the protonated O-atom in H1 and represents the first example of the phenolic Mn(i)-O linkage and a rare example of a "soft-homolysis" intermediate in the bond-weakening catalysis paradigm.

Resurgence of Organomanganese(I) Chemistry. Bidentate Manganese(I) Phosphine-Phenol(ate) Complexes.

As part of the United Nations 2019 celebration of the periodic table of elements, we are privileged to present our studies with the element manganese in this Forum Article series. Catalysis with organomanganese(I) complexes has recently emerged as an important area with the discovery that pincer manganese(I) complexes that can activate substrates through metal-ligand cooperative mechanisms are active (de)hydrogenation catalysts. However, this rapidly growing field faces several challenges, and we identify these in this Forum Article. Some of our efforts in addressing these challenges include using alternative precursors to Mn(CO)5Br to prepare manganese(I) dicarbonyl complexes, the latter of which is usually a component of active catalysts. Specifically, the synthesis of a new bidentate phosphine-phenol ligand along with its corresponding coordination chemistry of five new manganese(I) complexes is described. The complexes having two phenol-phenolate moieties interact with the secondary coordination sphere to enable facile loss of the bromido ligand and even one of the CO ligands to afford manganese(I) dicarbonyl centers.

Validity and effectiveness of paediatric early warning systems and track and trigger tools for identifying and reducing clinical deterioration in hospitalised children: a systematic review.

OBJECTIVE: To assess (1) how well validated existing paediatric track and trigger tools (PTTT) are for predicting adverse outcomes in hospitalised children, and (2) how effective broader paediatric early warning systems are at reducing adverse outcomes in hospitalised children. DESIGN: Systematic review. DATA SOURCES: British Nursing Index, Cumulative Index of Nursing and Allied Health Literature, Cochrane Central Register of Controlled Trials, Database of Abstracts of Reviews of Effectiveness, EMBASE, Health Management Information Centre, Medline, Medline in Process, Scopus and Web of Knowledge searched through May 2018. ELIGIBILITY CRITERIA: We included (1) papers reporting on the development or validation of a PTTT or (2) the implementation of a broader early warning system in paediatric units (age 0-18 years), where adverse outcome metrics were reported. Several study designs were considered. DATA EXTRACTION AND SYNTHESIS: Data extraction was conducted by two independent reviewers using template forms. Studies were quality assessed using a modified Downs and Black rating scale. RESULTS: 36 validation studies and 30 effectiveness studies were included, with 27 unique PTTT identified. Validation studies were largely retrospective case-control studies or chart reviews, while effectiveness studies were predominantly uncontrolled before-after studies. Metrics of adverse outcomes varied considerably. Some PTTT demonstrated good diagnostic accuracy in retrospective case-control studies (primarily for predicting paediatric intensive care unit transfers), but positive predictive value was consistently low, suggesting potential for alarm fatigue. A small number of effectiveness studies reported significant decreases in mortality, arrests or code calls, but were limited by methodological concerns. Overall, there was limited evidence of paediatric early warning system interventions leading to reductions in deterioration. CONCLUSION: There are several fundamental methodological limitations in the PTTT literature, and the predominance of single-site studies carried out in specialist centres greatly limits generalisability. With limited evidence of effectiveness, calls to make PTTT mandatory across all paediatric units are not supported by the evidence base. PROSPERO REGISTRATION NUMBER: CRD42015015326.

CO-Photolysis-Induced H-Atom Transfer from MnIO-H Bonds.

The formation of TEMPOH from a mixture of [Mn(CO)3(µ3-OH)]4 (1) and (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) is shown to occur through a light-initiated CO photolysis from 1 (illumination at 300-375 nm). One hypothesis is that the loss of carbon monoxide (CO) causes significant O-H bond weakening to render proton-coupled electron transfer (PCET) to TEMPO favorable. For instance, the ground-state O-H bond dissociation free energy (BDFEO-H) of 1 (computed with density functional theory and estimated using effective BDFE reagents) is too high to transfer an H-atom to TEMPO. We also demonstrate that TEMPO and 1 interact in the dark through a hydrogen-bonded "precomplex" (1···TEMPO). We suggest that the PCET reaction that forms TEMPOH is the result of a H-atom-transfer reaction that occurs immediately after photolysis of a CO ligand(s).

Pentacarbonylmethylmanganese(i) as a synthon for Mn(i) pincer catalysts.

Mn(i) complexes that enable metal-ligand cooperative substrate activation catalyze a range of transformations. Use of MeMn(CO)5 as a synthon in place of typical Mn(CO)5Br was explored and found to be quite versatile, generating catalytically active species in situ by activation of O-H, N-H, and even C-H bonds.

Magnetoelectric Radical Hydrocarbons.

The molecular radicals, systems with unpaired electrons of open-shell electronic structures, set the stage for a multidisciplinary science frontier relevant to the cooperative magnetic exchange interaction and magnetoelectric effect. Here ferroelectricity together with magnetic spin exchange coupling in molecular radical hydrocarbon solids is reported, representing a new class of magnetoelectrics. Electronic correlation through radical-radical interactions plays a decisive role in the coupling between magnetic and charge orders. A substantial photoconductance and visible-light photovoltaic effect are found in radical hydrocarbons. The ability to simultaneously control and retrieve the changes in magnetic and electrical responses opens up a new breadth of applications, such as radical magnetoelectrics, magnets, and optoelectronics.

Hole Extraction by Design in Photocatalytic Architectures Interfacing CdSe Quantum Dots with Topochemically Stabilized Tin Vanadium Oxide.

Tackling the complex challenge of harvesting solar energy to generate energy-dense fuels such as hydrogen requires the design of photocatalytic nanoarchitectures interfacing components that synergistically mediate a closely interlinked sequence of light-harvesting, charge separation, charge/mass transport, and catalytic processes. The design of such architectures requires careful consideration of both thermodynamic offsets and interfacial charge-transfer kinetics to ensure long-lived charge carriers that can be delivered at low overpotentials to the appropriate catalytic sites while mitigating parasitic reactions such as photocorrosion. Here we detail the theory-guided design and synthesis of nanowire/quantum dot heterostructures with interfacial electronic structure specifically tailored to promote light-induced charge separation and photocatalytic proton reduction. Topochemical synthesis yields a metastable ß-Sn0.23V2O5 compound exhibiting Sn 5s-derived midgap states ideally positioned to extract photogenerated holes from interfaced CdSe quantum dots. The existence of these midgap states near the upper edge of the valence band (VB) has been confirmed, and ß-Sn0.23V2O5/CdSe heterostructures have been shown to exhibit a 0 eV midgap state-VB offset, which underpins ultrafast subpicosecond hole transfer. The ß-Sn0.23V2O5/CdSe heterostructures are further shown to be viable photocatalytic architectures capable of efficacious hydrogen evolution. The results of this study underscore the criticality of precisely tailoring the electronic structure of semiconductor components to effect rapid charge separation necessary for photocatalysis.

Non-invasive ventilation for the management of children with bronchiolitis (NOVEMBR): a feasibility study and core outcome set development protocol.

BACKGROUND: Bronchiolitis is an acute lower respiratory infection which predominantly affects young children. Treatment for bronchiolitis is limited to supportive therapy. Nasal oxygen therapy is part of routine care, and delivery now incorporates varying levels of non-invasive continuous positive airway pressure and/or high-flow nasal cannula oxygen therapy. Despite wide clinical use, there remains a lack of evidence on the comparative effectiveness and safety of these interventions. Furthermore, research in this field is hampered by the use of multiple outcome measures in current clinical trials. METHODS/DESIGN: This mixed methods study includes a systematic review of outcome measures, telephone interviews with parents, focus group workshops and a Delphi survey with healthcare professionals and parents. These methods will be used to identify and prioritise outcomes for inclusion in a core outcome set and to explore issues pertinent to the design of a future randomised controlled trial comparing different modes of oxygen therapy for bronchiolitis. UK hospitals will also be contacted and asked to complete a survey to provide an overview of current practice to enable assessment of capability and capacity to run a future clinical trial. DISCUSSION: This study will facilitate the design of a future clinical trial of non-invasive ventilation in children with bronchiolitis which is acceptable to important stakeholders. Furthermore, core outcome set development will improve standardisation, measurement and reporting of clinically important outcomes in bronchiolitis. TRIAL REGISTRATION: ISRCTN Registry, ISRCTN75766048. Registered on 18 December 2017. This study was retrospectively registered in the ISRCTN Registry and on the Core Outcome Measures in Effectiveness Trials (COMET) Initiative database (15 September 2017).

Bisphosphine phenol and phenolate complexes of Mn(i): manganese(i) catalyzed Tishchenko reaction.

We synthesized new organomanganese complexes using the phenolic "pincer" type ligand H-POP. The coordination chemistry of H-POP with Mn(i) was explored, revealing a wide range of binding motifs. Finally, we found that complex 1 catalyzes the formation of benzyl benzoate from benzaldehyde in a Tishchenko reaction.

Deciphering the mechanism of O2 reduction with electronically tunable non-heme iron enzyme model complexes.

A homologous series of electronically tuned 2,2',2''-nitrilotris(N-arylacetamide) pre-ligands (H3LR ) were prepared (R = NO2, CN, CF3, F, Cl, Br, Et, Me, H, OMe, NMe2) and some of their corresponding Fe and Zn species synthesized. The iron complexes react rapidly with O2, the final products of which are diferric mu-oxo bridged species. The crystal structure of the oxidized product obtained from DMA solutions contain a structural motif found in some diiron proteins. The mechanism of iron mediated O2 reduction was explored to the extent that allowed us to construct an empirically consistent rate law. A Hammett plot was constructed that enabled insightful information into the rate-determining step and hence allows for a differentiation between two kinetically equivalent O2 reduction mechanisms.