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1. Computer‐Assisted 3D Structure Elucidation (CASE‐3D): The Structural Value of 2 J CH in Addition to 3 J CH Coupling Constants

   https://doi.org/10.1002/anie.201915103  

   Koos, Martin R. M. ; Navarro‐Vázquez, Armando ; Anklin, Clemens ; Gil, Roberto R. ( January 2020 , Angewandte Chemie International Edition)

   We present a method to use long‐range CH coupling constants to derive the correct diastereoisomer from the molecular constitution of small molecules. A set of 79²J_CHand³J_CHvalues collected from a single HSQMBC experiment on a sample of strychnine were used in the CASE‐3D (computer‐assisted 3D structure elucidation) protocol. In addition to the most commonly used³J_CHcoupling constants, the subset of 32²J_CHvalues alone showed an excellent degree of configuration selection. The study is mainly based on comparison of DFT‐calculated^2,3J_CHvalues with experimental ones, critical for the case of²J_CH. But the configuration selection also works well using³J_CHvalues predicted from a semi‐empirical Karplus‐based equation limited to H−C−C−C fragments. The robustness, shown using strychnine as a proof of concept, makes theJ‐based CASE‐3D analysis a viable option for the application in fields such as peptide and carbohydrate research, organic synthesis, natural‐product identification and analysis, as well as medicinal chemistry.

    

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2. The β‐Agostic Structure in (C 5 Me 5 ) 2 Sc(CH 2 CH 3 ): Solid‐State NMR Studies of (C 5 Me 5 ) 2 Sc−R (R=Me, Ph, Et)

   https://doi.org/10.1002/anie.201805738  

   Culver, Damien B. ; Huynh, Winn ; Tafazolian, Hosein ; Ong, Ta‐Chung ; Conley, Matthew P. ( July 2018 , Angewandte Chemie International Edition)

   Multinuclear solid‐state NMR studies of Cp*₂Sc−R (Cp*=pentamethylcyclopentadienyl; R=Me, Ph, Et) and DFT calculations show that the Sc−Et complex contains a β‐CH agostic interaction. The static central transition⁴⁵Sc NMR spectra show that the quadrupolar coupling constants (C_q) follow the trend of Ph≈Me>Et, indicating that the Sc−R bond is different in Cp*₂Sc−Et compared to the methyl and phenyl complexes. Analysis of the chemical shift tensor (CST) shows that the deshielding experienced by Cβ in Sc−CH₂CH₃is related to coupling between the filled σ_C‐Corbital and the vacantorbital.

    

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3. The β‐Agostic Structure in (C 5 Me 5 ) 2 Sc(CH 2 CH 3 ): Solid‐State NMR Studies of (C 5 Me 5 ) 2 Sc−R (R=Me, Ph, Et)

   https://doi.org/10.1002/ange.201805738  

   Culver, Damien B. ; Huynh, Winn ; Tafazolian, Hosein ; Ong, Ta‐Chung ; Conley, Matthew P. ( July 2018 , Angewandte Chemie)

   Multinuclear solid‐state NMR studies of Cp*₂Sc−R (Cp*=pentamethylcyclopentadienyl; R=Me, Ph, Et) and DFT calculations show that the Sc−Et complex contains a β‐CH agostic interaction. The static central transition⁴⁵Sc NMR spectra show that the quadrupolar coupling constants (C_q) follow the trend of Ph≈Me>Et, indicating that the Sc−R bond is different in Cp*₂Sc−Et compared to the methyl and phenyl complexes. Analysis of the chemical shift tensor (CST) shows that the deshielding experienced by Cβ in Sc−CH₂CH₃is related to coupling between the filled σ_C‐Corbital and the vacantorbital.

    

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4. 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)

   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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5. Solvothermal Synthesis of [Cr 7 S 8 (en) 8 Cl 2 ]Cl 3  ⋅ 2H 2 O with Magnetically Frustrated [Cr 7 S 8 ] 5+ Double‐Cubes**

   https://doi.org/10.1002/chem.202103761  

   Gamage, Eranga H. ; Clark, Judith K. ; Yazback, Maher ; Cheng, Hai‐Ping ; Shatruk, Michael ; Kovnir, Kirill ( December 2021 , Chemistry – A European Journal)

   A novel transition metal chalcohalide [Cr₇S₈(en)₈Cl₂]Cl₃ ⋅ 2H₂O, with [Cr₇S₈]⁵⁺dicubane cationic clusters, has been synthesized by a low temperature solvothermal method, using dimethyl sulfoxide (DMSO) and ethylenediamine (en) solvents. Ethylenediamine ligand exhibits bi‐ and monodentate coordination modes; in the latter case ethylenediamine coordinates to Cr atoms of adjacent clusters, giving rise to a 2D polymeric structure. Although magnetic susceptibility shows no magnetic ordering down to 1.8 K, a highly negative Weiss constant,θ=−224(2) K, obtained from Curie‐Weiss fit of inverse susceptibility, suggests strong antiferromagnetic (AFM) interactions betweenS=3/2 Cr(III) centers. Due to the complexity of the system with (2S+1)⁷=16384 microstates from seven Cr³⁺centers, a simplified model with only two exchange constants was used for simulations. Density‐functional theory (DFT) calculations yielded the two exchange constants to beJ₁=−21.4 cm⁻¹andJ₂=−30.2 cm⁻¹, confirming competing AFM coupling between the shared Cr³⁺center and the peripheral Cr³⁺ions of the dicubane cluster. The best simulation of the experimental data was obtained withJ₁=−20.0 cm⁻¹andJ₂=−21.0 cm⁻¹, in agreement with the slightly stronger AFM exchange within the triangles of the peripheral Cr³⁺ions as compared to the AFM exchange between the central and peripheral Cr³⁺ions. This compound is proposed as a synthon towards magnetically frustrated systems assembled by linking dicubane transition metal‐chalcogenide clusters into polymeric networks.

    

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