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Alkene hydroboration provides a convenient route to generate organoborane synthons and recent efforts to develop catalysts for this and many other organic transformations have involved a shift to Earth-abundant first row transition metals. Herein, we report the synthesis of a new bench-stable CoII precatalyst, (PPCF3P)CoI2 (1), which was found to function as a highly active alkene hydroboration catalyst in the presence of an activator. The substrate scope was probed through exploring a collection of electronically and sterically distinct alkenes with a wide range of substitution patterns and functional groups. A single species is spectroscopically observed during catalysis, and activation of the CoII precatalyst with KBEt3H in the presence of styrene and in the absence of HBpin affords this species, (PPCF3P)Co(h2-styrene)H (2), which has been isolated, characterized, and demonstrated to function as an active catalyst for alkene hydroboration in the absence of additional activators. A plausible mechanism involving a CoI-hydride active species is proposed based on catalytic and stoichiometric experiments. 

Abstract We report copper(II) and copper(III) trifluoromethyl complexes supported by a pyridinedicarboxamide ligand (L) as a platform for investigating the role of electron transfer in C(sp²)−H trifluoromethylation. While the copper(II) trifluoromethyl complex is unreactive towards (hetero)arenes, the formal copper(III) trifluoromethyl complex performs C(sp²)−H trifluoromethylation of a wide range of (hetero)arenes. Mechanistic studies using the copper(III) trifluoromethyl complex suggest that the mechanism of arene trifluoromethylation is substrate‐dependent. When the thermodynamic driving force for electron transfer is high, the reaction proceeds through a previously unidentified single electron transfer (SET) mechanism, where an initial electron transfer occurs between the substrate and oxidant prior to CF₃group transfer. Otherwise, a CF₃radical release/electrophilic aromatic substitution (S_EAr) mechanism is followed. These studies provide valuable insights into the role of strong oxidants and potential mechanistic dichotomy in Cu‐mediated C(sp²)−H trifluoromethylation. 

Abstract Maintaining stable drug concentrations in the bloodstream is a challenge for injectable hydrophobic progestin contraceptives. This work investigates porous silicon dioxide (pSiO₂) microparticles as a delivery vehicle for progestins via melt‐infiltration of drugs into the mesopores. The pSiO₂is prepared through electrochemical anodization of single‐crystalline silicon followed by thermal oxidation, yielding vertically oriented pores (≈50 nm diameter) with porosity varied (between 35–75%) to optimize drug loading and release. Among the progestins tested, etonogestrel and levonorgestrel (LNG) decompose near their melting points, preventing melt infiltration. However, addition of 20% cholesterol by mass suppresses the melting point of LNG sufficiently to enable loading without degradation. Mass loadings exceeding 50% (drug: drug + carrier) are achieved for segesterone acetate (SEG) and LNG, retaining drug crystallinity as confirmed by X‐ray diffraction. In vitro, both SEG and LNG‐loaded pSiO₂display sustained drug release for up to 3 months, with reduced burst release, more constant steady‐state concentrations, and a substantially reduced tail compared to pure LNG or SEG, or SEG loaded into pSiO₂from a chloroform solution. In a pilot in vivo study, SEG‐loaded pSiO₂microparticles are well tolerated in 20‐week‐old female rats over a 25‐week period, with no signs of toxicity. 

A (PNNP)Fe^IIcomplex is shown to catalyze the dimerization of terminal alkynesviaa metal–ligand cooperative mechanism. 

Dehydrogenation of the ligand backbone of a bis(amido)bis(phosphine) Co complex is achieved through hydrogen atom abstraction. The new unsaturated backbone of the tetradentate ligand renders the ligand in the resulting Co complex redox-active.