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1. Introduction of a (Ph ₃ P) ₂ Pt group into the rim of an open-cage fullerene by breaking a carbon–carbon bond

   https://doi.org/10.1039/D1CC04336F  

   Gralinski, Steven R.; Roy, Mrittika; Baldauf, Lilia M.; Olmstead, Marilyn M.; Balch, Alan L. (October 2021, Chemical Communications)

   Treatment of an open-cage fullerene, designated as MMK-9, with (Ph 3 P) 4 Pt in toluene solution at room temperature allows a (PPh 3 ) 2 Pt unit to be incorporated into the rim of the cage so that it becomes an integral part of the carbon cage skeleton. The structure of the adduct has been determined by single crystal X-ray diffraction and reveals that the platinum atom has planar PtC 2 P 2 coordination, rather than the usual η 2 -bonding to an intact C–C double bond of the fullerene. 

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2. Synthesis and crystallographic characterization of diphenylamide rare-earth metal complexes Ln (NPh ₂ ) ₃ (THF) ₂ and [(Ph ₂ N) ₂ Ln (μ-NPh ₂ )] ₂

   https://doi.org/10.1107/S2056989020009998  

   Palumbo, Chad T.; Kotyk, Christopher M.; Ziller, Joseph W.; Evans, William J. (September 2020, Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   Studies of the coordination chemistry between the diphenylamide ligand, NPh 2 , and the smaller rare-earth Ln III ions, Ln = Y, Dy, and Er, led to the structural characterization by single-crystal X-ray diffraction crystallography of both solvated and unsolvated complexes, namely, tris(diphenylamido-κ N )bis(tetrahydrofuran-κ O )yttrium(III), Y(NPh 2 ) 3 (THF) 2 or [Y(C 12 H 10 N) 3 (C 4 H 8 O) 2 ], 1-Y , and the erbium(III) (Er), 1-Er , analogue, and bis[μ-1κ N :2(η 6 )-diphenylamido]bis[bis(diphenylamido-κ N )yttrium(III)], [(Ph 2 N) 2 Y(μ-NPh 2 )] 2 or [Y 2 (C 12 H 10 N) 6 ], 2-Y , and the dysprosium(III) (Dy), 2-Dy , analogue. The THF ligands of 1-Er are modeled with disorder across two positions with occupancies of 0.627 (12):0.323 (12) and 0.633 (7):0.367 (7). Also structurally characterized was the tetrametallic Er III bridging oxide hydrolysis product, bis(μ-diphenylamido-κ 2 N : N )bis[μ-1κ N :2(η 6 )-diphenylamido]tetrakis(diphenylamido-κ N )di-μ 3 -oxido-tetraerbium(III) benzene disolvate, {[(Ph 2 N)Er(μ-NPh 2 )] 4 (μ-O) 2 }·(C 6 H 6 ) 2 or [Er 4 (C 12 H 10 N) 8 O 2 ]·2C 6 H 6 , 3-Er . The 3-Er structure was refined as a three-component twin with occupancies 0.7375:0.2010:0.0615. 

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3. Thermodynamic and kinetic studies of H ₂ and N ₂ binding to bimetallic nickel-group 13 complexes and neutron structure of a Ni(η ² -H ₂ ) adduct

   https://doi.org/10.1039/C9SC02018G  

   Cammarota, Ryan C.; Xie, Jing; Burgess, Samantha A.; Vollmer, Matthew V.; Vogiatzis, Konstantinos D.; Ye, Jingyun; Linehan, John C.; Appel, Aaron M.; Hoffmann, Christina; Wang, Xiaoping; et al (July 2019, Chemical Science)

   Understanding H 2 binding and activation is important in the context of designing transition metal catalysts for many processes, including hydrogenation and the interconversion of H 2 with protons and electrons. This work reports the first thermodynamic and kinetic H 2 binding studies for an isostructural series of first-row metal complexes: NiML, where M = Al ( 1 ), Ga ( 2 ), and In ( 3 ), and L = [N( o -(NCH 2 P i Pr 2 )C 6 H 4 ) 3 ] 3− . Thermodynamic free energies (Δ G °) and free energies of activation (Δ G ‡ ) for binding equilibria were obtained via variable-temperature 31 P NMR studies and lineshape analysis. The supporting metal exerts a large influence on the thermodynamic favorability of both H 2 and N 2 binding to Ni, with Δ G ° values for H 2 binding found to span nearly the entire range of previous reports. The non-classical H 2 adduct, (η 2 -H 2 )NiInL ( 3 -H 2 ), was structurally characterized by single-crystal neutron diffraction—the first such study for a Ni(η 2 -H 2 ) complex or any d 10 M(η 2 -H 2 ) complex. UV-Vis studies and TD-DFT calculations identified specific electronic structure perturbations of the supporting metal which poise NiML complexes for small-molecule binding. ETS-NOCV calculations indicate that H 2 binding primarily occurs via H–H σ-donation to the Ni 4p z -based LUMO, which is proposed to become energetically accessible as the Ni(0)→M( iii ) dative interaction increases for the larger M( iii ) ions. Linear free-energy relationships are discussed, with the activation barrier for H 2 binding (Δ G ‡ ) found to decrease proportionally for more thermodynamically favorable equilibria. The Δ G ° values for H 2 and N 2 binding to NiML complexes were also found to be more exergonic for the larger M( iii ) ions. 

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4. Evaluating Diazene to N ₂ Interconversion at Iron‐Sulfur Complexes

   https://doi.org/10.1002/chem.202304072  

   Hooper, Reagan X.; Wertz, Ashlee E.; Shafaat, Hannah S.; Holland, Patrick L. (March 2024, Chemistry – A European Journal)

   Abstract Biological N₂reduction occurs at sulfur‐rich multiiron sites, and an interesting potential pathway is concerted double reduction/ protonation of bridging N₂through PCET. Here, we test the feasibility of using synthetic sulfur‐supported diiron complexes to mimic this pathway. Oxidative proton transfer from μ‐η¹ : η¹‐diazene (HN=NH) is the microscopic reverse of the proposed N₂fixation pathway, revealing the energetics of the process. Previously, Sellmann assigned the purple metastable product from two‐electron oxidation of [{Fe²⁺(PPr₃)L¹}₂(μ‐η¹ : η¹‐N₂H₂)] (L¹=tetradentate SSSS ligand) at −78 °C as [{Fe²⁺(PPr₃)L¹}₂(μ‐η¹ : η¹‐N₂)]²⁺, which would come from double PCET from diazene to sulfur atoms of the supporting ligands. Using resonance Raman, Mössbauer, NMR, and EPR spectroscopies in conjunction with DFT calculations, we show that the product is not an N₂complex. Instead, the data are most consistent with the spectroscopically observed species being the mononuclear iron(III) diazene complex [{Fe(PPr₃)L¹}(η²‐N₂H₂)]⁺. Calculations indicate that the proposed double PCET has a barrier that is too high for proton transfer at the reaction temperature. Also, PCET from the bridging diazene is highly exergonic as a result of the high Fe^3+/2+redox potential, indicating that the reverse N₂protonation would be too endergonic to proceed. This system establishes the “ground rules” for designing reversible N₂/N₂H₂interconversion through PCET, such as tuning the redox potentials of the metal sites. 

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5. Synthesis and characterization of a tert- butyl ester-substituted titanocene dichloride: ^t-BuOOC Cp ₂ TiCl ₂

   https://doi.org/10.1107/S2056989020011834  

   McCarthy, Jackson S.; McMillen, Colin D.; Pienkos, Jared A.; Wagenknecht, Paul S. (October 2020, Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   Bis[η 5 -( tert -butoxycarbonyl)cyclopentadienyl]dichloridotitanium(IV), [Ti(C 10 H 13 O 2 ) 2 Cl 2 ], was synthesized from LiCp COO t -Bu using TiCl 4 , and was characterized by single-crystal X-ray diffraction and 1 H NMR spectroscopy. The distorted tetrahedral geometry about the central titanium atom is relatively unchanged compared to Cp 2 TiCl 2 . The complex exhibits elongation of the titanium–cyclopentadienyl centroid distances [2.074 (3) and 2.070 (3) Å] and a contraction of the titanium–chlorine bond lengths [2.3222 (10) Å and 2.3423 (10) Å] relative to Cp 2 TiCl 2 . The dihedral angle formed by the planes of the Cp rings [52.56 (13)°] is smaller than seen in Cp 2 TiCl 2 . Both ester groups extend from the same side of the Cp rings, and occur on the same side of the complex as the chlorido ligands. The complex may serve as a convenient synthon for titanocene complexes with carboxylate anchoring groups for binding to metal oxide substrates. 

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