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1. Hydrogen Dissolution Mechanisms in Bridgmanite by First‐Principles Calculations and Infrared Spectroscopy

   https://doi.org/10.1029/2024JB030403  

   Zhang, Yanyao; Tsuchiya, Jun; Li, ChingChien; Ye, Zefang; Yan, Wei; Okuchi, Takuo; Karato, Shun‐ichiro; Kung, Jennifer; Lin, Jung‐Fu (January 2025, Journal of Geophysical Research: Solid Earth)

   Abstract Understanding hydrogen dissolution mechanisms in bridgmanite (Bgm), the most abundant mineral in the lower mantle, is essential for understanding water storage and rheological and transport properties in the region. However, interpretations of O‐H bands in Fourier transform infrared spectroscopy (FTIR) spectra of Bgm crystals remain uncertain. We conducted density functional theory (DFT) calculations on vibrational characteristics of O‐H dipoles and performed polarized FTIR measurements to address this issue. DFT calculations for four substitution models—Mg vacancies, Si vacancies, Al³⁺ + H⁺substitution for Si⁴⁺, and Al substitution with Mg vacancies—reveal distinct O‐H bands with different polarizations. Deconvolution of polarized FTIR spectra on Mg_0.88Fe²⁺_0.035Fe³⁺_0.065Al_0.14Si_0.90O₃and Mg_0.95Fe²⁺_0.033Fe³⁺_0.027Al_0.04Si_0.96O₃crystals shows five major O‐H bands with distinct polarizations along principal crystallographic axes. These experimental and calculated results attribute O‐H bands centered at 3,463–3,480, 2,913–2,924, and 2,452–2,470 cm⁻¹to Mg vacancies, Si vacancies, and Al³⁺ + H⁺substitution for Si⁴⁺, respectively. The total absorbance coefficient of bridgmanite was calculated to be 82,702(6,217) L/mol/cm². Mg and Si vacancies account for 43%–74% of the total water content, making them dominant hydrogen dissolution mechanisms in Bgm. The band frequencies for the Mg and Si vacancies in Bgm are drastically different from those in olivine and ringwoodite, corresponding to the significant changes in O‐H bond strengths and in the Si and Mg coordination environments from upper‐mantle to lower‐mantle minerals. These results highlight the need to incorporate hydrogen dissolution mechanisms in Bgm for understanding electrical conductivity and rheology of the lower mantle. 

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2. Solid‐State Investigation, Storage, and Separation of Pyrophoric PH ₃ and P ₂ H ₄ with α‐Mg Formate

   https://doi.org/10.1002/anie.202217534  

   Widera, Anna; Thöny, Debora; Aebli, Marcel; Oppenheim, Julius Jacob; Andrews, Justin L.; Eiler, Frederik; Wörle, Michael; Schönberg, Hartmut; Weferling, Norbert; Dincǎ, Mircea; et al (February 2023, Angewandte Chemie International Edition)

   Abstract Phosphane, PH₃—a highly pyrophoric and toxic gas—is frequently contaminated with H₂and P₂H₄, which makes its handling even more dangerous. The inexpensive metal–organic framework (MOF) magnesium formate, α‐[Mg(O₂CH)₂], can adsorb up to 10 wt % of PH₃. The PH₃‐loaded MOF, PH₃@α‐[Mg(O₂CH)₂], is a non‐pyrophoric, recoverable material that even allows brief handling in air, thereby minimizing the hazards associated with the handling and transport of phosphane. α‐[Mg(O₂CH)₂] further plays a critical role in purifying PH₃from H₂and P₂H₄: at 25 °C, H₂passes through the MOF channels without adsorption, whereas PH₃adsorbs readily and only slowly desorbs under a flow of inert gas (complete desorption time≈6 h). Diphosphane, P₂H₄, is strongly adsorbed and trapped within the MOF for at least 4 months. P₂H₄@α‐[Mg(O₂CH)₂] itself is not pyrophoric and is air‐ and light‐stable at room temperature. 

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3. Synthesis of a “Masked” Terminal Zinc Sulfide and Its Reactivity with Brønsted and Lewis Acids

   https://doi.org/10.1002/anie.202002364  

   Baeza Cinco, Miguel Á.; Wu, Guang; Kaltsoyannis, Nikolas; Hayton, Trevor W. (April 2020, Angewandte Chemie International Edition)

   Abstract The “masked” terminal Zn sulfide, [K(2.2.2‐cryptand)][^MeLZn(S)] (2) (^MeL={(2,6‐ⁱPr₂C₆H₃)NC(Me)}₂CH), was isolated via reaction of [^MeLZnSCPh₃] (1) with 2.3 equivalents of KC₈in THF, in the presence of 2.2.2‐cryptand, at −78 °C. Complex2reacts readily with PhCCH and N₂O to form [K(2.2.2‐cryptand)][^MeLZn(SH)(CCPh)] (4) and [K(2.2.2‐cryptand)][^MeLZn(SNNO)] (5), respectively, displaying both Brønsted and Lewis basicity. In addition, the electronic structure of2was examined computationally and compared with the previously reported Ni congener, [K(2.2.2‐cryptand)][^tBuLNi(S)] (^tBuL={(2,6‐ⁱPr₂C₆H₃)NC(^tBu)}₂CH). 

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4. Crystal structure of (1,4,7,10,13,16-hexaoxacyclooctadecane-κ ⁶ O )potassium-μ-oxalato-triphenylstannate(IV), the first reported 18-crown-6-stabilized potassium salt of triphenyloxalatostannate

   https://doi.org/10.1107/S2056989024007758  

   Song, Xueqing; Li, William; Torres, Yolanda; Greaves, Tazena (September 2024, Acta Crystallographica Section E Crystallographic Communications)

   The title complex, (1,4,7,10,13,16-hexaoxacyclooctadecane-1κ⁶O)(μ-oxalato-1κ²O¹,O²:2κ²O^1′,O^2′)triphenyl-2κ³C-potassium(I)tin(IV), [KSn(C₆H₅)₃(C₂O₄)(C₁₂H₂₄O₆)] or K[18-Crown-6][(C₆H₅)₃SnO₄C₂], was synthesized. The complex consists of a potassium cation coordinated to the six oxygen atoms of a crown ether molecule and the two oxygen atoms of the oxalatotriphenylstannate anion. It crystallizes in the monoclinic crystal system within the space groupP2₁. The tin atom is coordinated by one chelating oxalate ligand and three phenyl groups, forming acis-trigonal–bipyramidal geometry around the tin atom. The cations and anions form ion pairs, linked through carbonyl coordination to the potassium atoms. The crystal structure features C—H...O hydrogen bonds between the oxygen atoms of the oxalate group and the hydrogen atoms of the phenyl groups, resulting in an infinite chain structure extending alonga-axis direction. The primary inter-chain interactions are van der Waals forces. 

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5. Copper‐Catalyzed C(sp ³ )−H Amidation: Sterically Driven Primary and Secondary C−H Site‐Selectivity

   https://doi.org/10.1002/anie.201810556  

   Bakhoda, Abolghasem; Jiang, Quan; Badiei, Yosra M.; Bertke, Jeffery A.; Cundari, Thomas R.; Warren, Timothy H. (February 2019, Angewandte Chemie International Edition)

   Abstract Undirected C(sp³)−H functionalization reactions often follow site‐selectivity patterns that mirror the corresponding C−H bond dissociation energies (BDEs). This often results in the functionalization of weaker tertiary C−H bonds in the presence of stronger secondary and primary bonds. An important, contemporary challenge is the development of catalyst systems capable of selectively functionalizing stronger primary and secondary C−H bonds over tertiary and benzylic C−H sites. Herein, we report a Cu catalyst that exhibits a high degree of primary and secondary over tertiary C−H bond selectivity in the amidation of linear and cyclic hydrocarbons with aroyl azides ArC(O)N₃. Mechanistic and DFT studies indicate that C−H amidation involves H‐atom abstraction from R‐H substrates by nitrene intermediates [Cu](κ²‐N,O‐NC(O)Ar) to provide carbon‐based radicals R^.and copper(II)amide intermediates [Cu^II]‐NHC(O)Ar that subsequently capture radicals R^.to form products R‐NHC(O)Ar. These studies reveal important catalyst features required to achieve primary and secondary C−H amidation selectivity in the absence of directing groups. 

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