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1. 10 ⁶ -fold faster C–H bond hydroxylation by a Co ^III,IV ₂ (µ-O) ₂ complex [via a Co ^III ₂ (µ-O)(µ-OH) intermediate] versus its Fe ^III Fe ^IV analog

   https://doi.org/10.1073/pnas.2307950120  

   Li, Yan; Abelson, Chase; Que, Lawrence; Wang, Dong (December 2023, Proceedings of the National Academy of Sciences)

   The hydroxylation of C–H bonds can be carried out by the high-valent Co^III,IV₂(µ-O)₂complex2asupported by the tetradentate tris(2-pyridylmethyl)amine ligand via a Co^III₂(µ-O)(µ-OH) intermediate (3a). Complex3acan be independently generated either by H-atom transfer (HAT) in the reaction of2awith phenols as the H-atom donor or protonation of its conjugate base, the Co^III₂(µ-O)₂complex1a. Resonance Raman spectra of these three complexes reveal oxygen-isotope-sensitive vibrations at 560 to 590 cm⁻¹associated with the symmetric Co–O–Co stretching mode of the Co₂O₂diamond core. Together with a Co•••Co distance of 2.78(2) Å previously identified for1aand2aby Extended X-ray Absorption Fine Structure (EXAFS) analysis, these results provide solid evidence for their “diamond core” structural assignments. The independent generation of3aallows us to investigate HAT reactions of2awith phenols in detail, measure the redox potential and pK_aof the system, and calculate the O–H bond strength (D_O–H) of3ato shed light on the C–H bond activation reactivity of2a. Complex3ais found to be able to transfer its hydroxyl ligand onto the trityl radical to form the hydroxylated product, representing a direct experimental observation of such a reaction by a dinuclear cobalt complex. Surprisingly, reactivity comparisons reveal2ato be 10⁶-fold more reactive in oxidizing hydrocarbon C–H bonds than corresponding Fe^III,IV₂(µ-O)₂and Mn^III,IV₂(µ-O)₂analogs, an unexpected outcome that raises the prospects for using Co^III,IV₂(µ-O)₂species to oxidize alkane C–H bonds. 

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2. Organo‐Functionalized Lacunary Double Cubane‐Type Oxometallates: Synthesis, Structure, and Properties of [(M ^II Cl) ₂ (V ^IV O) ₂ {((HOCH ₂ CH ₂ )(H)N(CH ₂ CH ₂ O))(HN(CH ₂ CH ₂ O) ₂ )} ₂ ] (M=Co, Zn)

   https://doi.org/10.1002/chem.202301389  

   Shuaib, Damola T.; Swenson, LaSalle; Kaduk, James A.; Chang, Tieyan; Chen, Yu‐Sheng; McNeely, James; Khan, M. Ishaque (October 2023, Chemistry – A European Journal)

   Abstract Organofunctionalized tetranuclear clusters [(M^IICl)₂(V^IVO)₂{((HOCH₂CH₂)(H)N(CH₂CH₂O))(HN(CH₂CH₂O)₂)}₂] (1, M=Co,2: M=Zn) containing an unprecedented oxometallacyclic {M₂V₂Cl₂N₄O₈} (M=Co, Zn) framework have been prepared by solvothermal reactions. The new oxo‐alkoxide compounds were fully characterized by spectroscopic methods, magnetic susceptibility measurement, DFT and ab initio computational methods, and complete single‐crystal X‐ray diffraction structure analysis. The isostructural clusters are formed of edge‐sharing octahedral {VO₅N} and trigonal bipyramidal {MO₃NCl} units. Diethanolamine ligates the bimetallic lacunary double cubane core of1and2in an unusual two‐mode fashion, unobserved previously. In the crystalline state, the clusters of1and2are joined by hydrogen bonds to form a three‐dimensional network structure. Magnetic susceptibility data indicate weakly antiferromagnetic interactions between the vanadium centers [J_iso(V^IV−V^IV)=−5.4(1); −3.9(2) cm⁻¹], and inequivalent antiferromagnetic interactions between the cobalt and vanadium centers [J_iso(V^IV−Co^II)=−12.6 and −7.5 cm⁻¹] contained in1. 

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3. Insertion of CO ₂ Mediated by a (Xantphos)Ni ^I –Alkyl Species

   https://doi.org/10.1002/anie.201906005  

   Diccianni, Justin B.; Hu, Chunhua T.; Diao, Tianning (August 2019, Angewandte Chemie International Edition)

   Abstract The incorporation of CO₂into organometallic and organic molecules represents a sustainable way to prepare carboxylates. The mechanism of reductive carboxylation of alkyl halides has been proposed to proceed through the reduction of Ni^IIto Ni^Iby either Zn or Mn, followed by CO₂insertion into Ni^I‐alkyl species. No experimental evidence has been previously established to support the two proposed steps. Demonstrated herein is that the direct reduction of (tBu‐Xantphos)Ni^IIBr₂by Zn affords Ni^Ispecies. (tBu‐Xantphos)Ni^I‐Me and (tBu‐Xantphos)Ni^I‐Et complexes undergo fast insertion of CO₂at 22 °C. The substantially faster rate, relative to that of Ni^IIcomplexes, serves as the long‐sought‐after experimental support for the proposed mechanisms of Ni‐catalyzed carboxylation reactions. 

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4. Influence of Temperature and CO ₂ On Plasma‐membrane Permeability to CO ₂ and HCO ₃ ⁻ in the Marine Haptophytes Emiliania huxleyi and Calcidiscus leptoporus (Prymnesiophyceae)

   https://doi.org/10.1111/jpy.13017  

   Blanco‐Ameijeiras, Sonia; Stoll, Heather M.; Zhang, Hongrui; Hopkinson, Brian M.; Raven, ed., J. (June 2020, Journal of Phycology)

   Membrane permeabilities to CO₂and HCO₃⁻constrain the function of CO₂concentrating mechanisms that algae use to supply inorganic carbon for photosynthesis. In diatoms and green algae, plasma membranes are moderately to highly permeable to CO₂but effectively impermeable to HCO₃⁻. Here, CO₂and HCO₃⁻membrane permeabilities were measured using an¹⁸O‐exchange technique on two species of haptophyte algae,Emiliania huxleyiandCalcidiscus leptoporus, which showed that the plasma membranes of these species are also highly permeable to CO₂(0.006–0.02 cm · s⁻¹) but minimally permeable to HCO₃⁻. Increased temperature and CO₂generally increased CO₂membrane permeabilities in both species, possibly due to changes in lipid composition or CO₂channel proteins. Changes in CO₂membrane permeabilities showed no association with the density of calcium carbonate coccoliths surrounding the cell, which could potentially impede passage of compounds. Haptophyte plasma‐membrane permeabilities to CO₂were somewhat lower than those of diatoms but generally higher than membrane permeabilities of green algae. One caveat of these measurements is that the model used to interpret¹⁸O‐exchange data assumes that carbonic anhydrase, which catalyzes¹⁸O‐exchange, is homogeneously distributed in the cell. The implications of this assumption were tested using a two‐compartment model with an inhomogeneous distribution of carbonic anhydrase to simulate¹⁸O‐exchange data and then inferring plasma‐membrane CO₂permeabilities from the simulated data. This analysis showed that the inferred plasma‐membrane CO₂permeabilities are minimal estimates but should be quite accurate under most conditions. 

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5. Non‐Aqueous Electrochemical CO ₂ Reduction to Multivariate C ₂ ‐Products Over Single Atom Catalyst at Current Density up to 100 mA cm ⁻²

   https://doi.org/10.1002/smll.202408010  

   Bhawnani, Rajan_R; Sartape, Rohan; Gande, Vamsi_V; Barsoum, Michael_L; Kallon, Elias_M; Reis, Roberto_dos; Dravid, Vinayak_P; Singh, Meenesh_R (December 2024, Small)

   Abstract Electrochemical CO₂reduction reaction (CO₂‐RR) in non‐aqueous electrolytes offers significant advantages over aqueous systems, as it boosts CO₂solubility and limits the formation of HCO₃⁻and CO₃²⁻anions. Metal–organic frameworks (MOFs) in non‐aqueous CO₂‐RR makes an attractive system for CO₂capture and conversion. However, the predominantly organic composition of MOFs limits their electrical conductivity and stability in electrocatalysis, where they suffer from electrolytic decomposition. In this work, electrically conductive and stable Zirconium (Zr)‐based porphyrin MOF, specifically PCN‐222, metalated with a single‐atom Cu has been explored, which serves as an efficient single‐atom catalyst (SAC) for CO₂‐RR. PCN‐ 222(Cu) demonstrates a substantial enhancement in redox activity due to the synergistic effect of the Zr matrix and the single‐atom Cu site, facilitating complete reduction of C₂species under non‐aqueous electrolytic conditions. The current densities achieved (≈100 mA cm⁻²) are 4–5 times higher than previously reported values for MOFs, with a faradaic efficiency of up to 40% for acetate production, along with other multivariate C₂products, which have never been achieved previously in non‐aqueous systems. Characterization using X‐ray and various spectroscopic techniques, reveals critical insights into the role of the Zr matrix and Cu sites in CO₂reduction, benchmarking PCN‐222(Cu) for MOF‐based SAC electrocatalysis. 

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