Probing the viability of oxo-coupling pathways in iridium-catalyzed oxygen evolution

[Image: see text] A series of Cp*Ir(III) dimers have been synthesized to elucidate the mechanistic viability of radical oxo-coupling pathways in iridium-catalyzed O(2) evolution. The oxidative stability of the precursors toward nanoparticle formation and their oxygen evolution activity have been investigated and compared to suitable monomeric analogues. We found that precursors bearing monodentate NHC ligands degraded to form nanoparticles (NPs), and accordingly their O(2) evolution rates were not significantly influenced by their nuclearity or distance between the two metals in the dimeric precursors. A doubly chelating bis-pyridine–pyrazolide ligand provided an oxidation-resistant ligand framework that allowed a more meaningful comparison of catalytic performance of dimers with their corresponding monomers. With sodium periodate (NaIO(4)) as the oxidant, the dimers provided significantly lower O(2) evolution rates per [Ir] than the monomer, suggesting a negative interaction instead of cooperativity in the catalytic cycle. Electrochemical analysis of the dimers further substantiates the notion that no radical oxyl-coupling pathways are accessible. We thus conclude that the alternative path, nucleophilic attack of water on high-valent Ir-oxo species, may be the preferred mechanistic pathway of water oxidation with these catalysts, and bimolecular oxo-coupling is not a valid mechanistic alternative as in the related ruthenium chemistry, at least in the present system

Using social and behavioural science to support COVID-19 pandemic response

The COVID-19 pandemic represents a massive global health crisis. Because the crisis requires large-scale behaviour change and places significant psychological burdens on individuals, insights from the social and behavioural sciences can be used to help align human behavior with the recommendations of epidemiologists and public health experts. Here we discuss evidence from a selection of research topics relevant to pandemics, including work on navigating threats, social and cultural influences on behaviour, science communication, moral decision-making, leadership, and stress and coping. In each section, we note the nature and quality of prior research, including uncertainty and unsettled issues. We identify several insights for effective response to the COVID-19 pandemic, and also highlight important gaps researchers should move quickly to fill in the coming weeks and months

Electron-rich CpIr(biphenyl-2,2′-diyl) complexes with π-accepting carbon donor ligands

Cp*Ir III and CpIr III complexes have attracted interest as catalysts for oxidative transformations, and highly oxidizing iridium species are postulated as key intermediates in both catalytic water and C-H bond oxidation. Strongly electron-donating ligand sets have been shown to stabilize Ir IV complexes. We describe the synthesis and reactivity of complexes containing the CpIr(biphenyl-2,2′-diyl) moiety stabilized by a series of strong donor carbon-based ligands. The oxidation chemistry of these complexes has been characterized electrochemically, and a singly oxidized Ir IV species has been observed by X-band EPR for the complex CpIr(biph)(p-CNCH 2SO 2C 6H 4CH 3). © 2012 American Chemical Society

Electron-Rich CpIr(biphenyl-2,2′-diyl) Complexes with π‑Accepting Carbon Donor Ligands

Cp*Ir^III and CpIr^III complexes have attracted interest as catalysts for oxidative transformations, and highly oxidizing iridium species are postulated as key intermediates in both catalytic water and C–H bond oxidation. Strongly electron-donating ligand sets have been shown to stabilize Ir^IV complexes. We describe the synthesis and reactivity of complexes containing the CpIr­(biphenyl-2,2′-diyl) moiety stabilized by a series of strong donor carbon-based ligands. The oxidation chemistry of these complexes has been characterized electrochemically, and a singly oxidized Ir^IV species has been observed by X-band EPR for the complex CpIr­(biph)­(<i>p-</i>CNCH₂SO₂C₆H₄CH₃)

Unfounded beliefs among teachers: The interactive role of rationality priming and cognitive ability

Previous research suggests that unfounded beliefs (UB)—such as conspiracist beliefs and beliefs in the supernatural—stem from similar cognitive and motivational mechanisms. More specifically, it has been demonstrated that cognitive ability is negatively associated with UB but only among individuals who value epistemic rationality. The present study goes beyond previous correlational studies by examining whether the negative association between cognitive ability and UB can be strengthened through a subtle rationality prime. In a large scale online experiment (N = 762 French teachers), we demonstrate that priming rationality (vs. control) does enhance the negative relationship between cognitive ability and adherence to supernatural beliefs, as well as conspiracy mentality (d = 0.2). This effect was not obtained for illusory pattern perception. This study's usefulness as a “proof of concept” for future interventions aimed at reducing UB prevalence among the general public is discussed

Iridium-catalysed arylation of C-H bonds enabled by oxidatively induced reductive elimination

Direct arylation of C-H bonds is in principle a powerful way of preparing value-added molecules that contain carbon-aryl fragments. Unfortunately, currently available synthetic methods are not sufficiently effective to be practical alternatives to conventional cross-coupling reactions. We propose that the main problem lies in the late portion of the catalytic cycle where reductive elimination gives the desired carbon-aryl bond. Accordingly, we have developed a strategy where the Ir(III) centre of the key intermediate is first oxidized to Ir(IV). Density functional theory calculations indicate that the barrier to reductive elimination is reduced by nearly 19 kcal mol-1 for this oxidized complex compared with that of its Ir(III) counterpart. Various experiments confirm this prediction, affording a new methodology capable of directly arylating C-H bonds at room temperature with a broad substrate scope and in good yields. This work highlights how the oxidation states of intermediates can be targeted deliberately to catalyse an otherwise impossible reaction. ©2018 Macmillan Publishers Limited, part of Springer Nature. (c) All rights reserve