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We report that the cationic iridium complex (iPrPCP)IrH+ catalyzes the transfer-dehydrogenation of alkanes to give alkenes, and hydrogen isotope exchange (HIE) of alkanes and arenes. Contrary to established selectivity trends found for C-H activation by transition metal complexes, strained cycloalkanes, including cyclopentane, cycloheptane, and cyclooctane, undergo C-H addition much more readily than n-alkanes, which in turn are much more reactive than cyclohexane. Aromatic C-H bonds also undergo H/D exchange much less rapidly than those of the strained cycloalkanes, but much more favorably than cyclohexane. The order of reactivity toward dehydrogenation correlates qualitatively with the reaction thermodynamics, but the magnitude is much greater than can be explained by thermodynamics. Accordingly, the cycloalkenes corresponding to the strained cycloalkanes undergo hydrogenation much more readily than cyclohexene, despite the less favorable thermodynamics of such hydrogenations. Computational (DFT) studies allow rationalization of the origin of reactivity and the unusual selectivity. Specifically, the initial C-H addition is strongly assisted by β-agostic interactions, which are particularly favorable for the strained cycloalkanes. Subsequent to β-C-H addition, the H atom of the β-agostic C-H bond is transferred directly to the hydride ligand of (iPrPCP)IrH+, to give a dihydrogen ligand. The overall processes, C-H addition and β-H-transfer to hydride, are calculated to generally have minima on the IRC surface although not necessarily on the enthalpy or free energy surfaces; these minima are extremely shallow, such that the 1,2-dehydrogenations are effectively concerted although asynchronous. 

Abstract Bis‐porphyrin nanocages (M₂BiCage, M = FeCl, Co, Zn) and their host‐guest complexes with C₆₀and C₇₀were used to examine how molecular porosity and interactions with carbon nanomaterials affect the CO₂reduction activity of metalloporphyrin electrocatalysts. The cages were found to adsorb on carbon black to provide electrocatalytic inks with excellent accessibilities of the metal sites (≈50%) even at high metal loadings (2500 nmol cm⁻²), enabling good activity for reducing CO₂to CO. A complex of C₇₀bound inside(FeCl)₂BiCageachieves high current densities for CO formation at low overpotentials (|j_CO| >7 mA cm⁻²,η= 320 mV; >13.5 mA cm⁻²,η= 520 mV) with ≥95% Faradaic efficiency (FE_CO), andCo₂BiCageachieves high turnover frequencies (≈1300 h⁻¹,η= 520 mV) with 90% FE_CO. In general, blocking the pore with C₆₀or C₇₀improves the catalytic performance of(FeCl)₂BiCageand has only small effects onCo₂BiCage, indicating that the good catalytic properties of the cages cannot be attributed to their internal pores. Neither enhanced electron transfer rates nor metal‐fullerene interactions appear to underlie the ability of C₆₀/C₇₀to improve the performance of(FeCl)₂BiCage, in contrast to effects often proposed for other carbon nanosupports. 

The African naked mole rat (Heterocephalus glaber) is a small, eusocial rodent that lives in large colonies consisting of up to 295 individuals. Their skin is pink and translucent, and naked mole rats have a distinct set of incisors that protrude externally from the mouth so that they can close their lips behind their teeth while using the teeth to dig tunnels, toilets, and nest chambers. They construct and inhabit complex underground tunnel systems in the Horn of Africa where they are protected from climate extremes and predators on the surface, but still face limited resources (sparsely distributed food), and a biologically challenging environment where there is a depletion of oxygen and an accumulation of carbon dioxide from many respirating individuals living in an unventilated space. This is particularly an issue in the communal nest chambers where animals gather to huddle and sleep. Data from Zions et al. show that the nest chambers in colonies of captive naked mole rats have significantly, and substantially higher concentrations of CO2 compared to other compartments in the housing system. They also showed that on average, colony members spent more than 70% of their time in the nest chamber, exposed to elevated CO2. Naked mole rats have a multitude of biological adaptations that make them specialized for life in humid, congested, poorly ventilated burrows. Subsequently, this species is a fascinating and important nontraditional model for biomedical research. Studies have focused on topics such as tolerance to hypoxia and hypercapnia, extreme longevity, resistance to cancer, and insensitivity to chemical pain. One remarkable feature that naked mole rats display is the lack of Substance P from their peripheral nerves. Substance P is associated with pain from a variety of irritants such as carbon dioxide (CO2), acid, capsaicin, and ammonia, as well as itch-like pruritogen, like histamines. Lack of Substance P is presumably an adaptation to reduce the negative effects of living in a high CO2 atmosphere, which would cause a burning sensation in the nasal cavity and around the eyes, as well as acidosis in the lungs that causes pulmonary edema. This chapter reviews how this feature affects their physiology and behavior. For example, naked mole rats show a blunted response to inflammatory pain, complete insensitivity to irritants such as capsaicin, ammonia, and acid, and they do not show a scratching response to histamine. 

We report a family of cobalt complexes based on bidentate phosphine ligands with two, one, or zero pendent amine groups in the ligand backbone. The pendent amine complexes are active electrocatalysts for the formate oxidation reaction, generating CO2 with near-quantitative faradaic efficiency at moderate overpotentials (0.45−0.57 V in acetonitrile). Thermodynamic measurements reveal that these complexes are energetically primed for formate oxidation via hydride transfer to the cobalt center, followed by deprotonation of the resulting cobalt-hydride by formate acting as a base. The complex featuring a single pendent amine arm is the fastest electrocatalyst in this series, with an observed rate constant for formate oxidation of 135 ± 8 h−1 at 25 °C, surpassing the activity of the bis-pendent amine analogue. Electrocatalytic turnover is not observed for the complex with no pendent amine groups: decomposition of the complex is evident in the presence of high formate concentrations. Thus, the application of thermodynamic considerations to electrocatalyst design is demonstrated as a successful strategy, while also highlighting the delicate balance of ligand properties necessary for achieving productive turnover. 

Version control systems typically rely on apatch language, heuristicpatch synthesis algorithmslike diff, andthree-way merge algorithms. Standard patch languages and merge algorithms often fail to identify conflicts correctly when there are multiple edits to one line of code or code is relocated. This paper introduces Grove, a collaborative structure editor calculus that eliminates patch synthesis and three-way merge algorithms entirely. Instead, patches are derived directly from the log of the developer’s edit actions and all edits commute, i.e. the repository state forms a commutative replicated data type (CmRDT). To handle conflicts that can arise due to code relocation, the core datatype in Grove is a labeled directed multi-graph with uniquely identified vertices and edges. All edits amount to edge insertion and deletion, with deletion being permanent. To support tree-based editing, we define a decomposition from graphs intogroves, which are a set of syntax trees with conflicts—including local, relocation, and unicyclic relocation conflicts—represented explicitly using holes and references between trees. Finally, we define a type error localization system for groves that enjoys atotalityproperty, i.e. all editor states in Grove are statically meaningful, so developers can use standard editor services while working to resolve these explicitly represented conflicts. The static semantics is defined as a bidirectional marking system in line with recent work, with gradual typing employed to handle situations where errors and conflicts prevent type determination. We then layer on a unification-based type inference system to opportunistically fill type holes and fail gracefully when no solution exists. We mechanize the metatheory of Grove using the Agda theorem prover. We implement these ideas as theGrove Workbench, which generates the necessary data structures and algorithms in OCaml given a syntax tree specification.