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1. Delocalization tunable by ligand substitution in [L ₂ Al] ⁿ⁻ complexes highlights a mechanism for strong electronic coupling

   https://doi.org/10.1039/D0SC02812F  

   Arnold, Amela; Sherbow, Tobias J.; Bohanon, Amanda M.; Sayler, Richard I.; Britt, R. David; Smith, Allison M.; Fettinger, James C.; Berben, Louise A. (January 2021, Chemical Science)

   null (Ed.)

   Ligand-based mixed valent (MV) complexes of Al( iii ) incorporating electron donating (ED) and electron withdrawing (EW) substituents on bis(imino)pyridine ligands (I 2 P) have been prepared. The MV states containing EW groups are both assigned as Class II/III, and those with ED functional groups are Class III and Class II/III in the (I 2 P − )(I 2 P 2− )Al and [(I 2 P 2− )(I 2 P 3− )Al] 2− charge states, respectively. No abrupt changes in delocalization are observed with ED and EW groups and from this we infer that ligand and metal valence p-orbitals are well-matched in energy and the absence of LMCT and MLCT bands supports the delocalized electronic structures. The MV ligand charge states (I 2 P − )(I 2 P 2− )Al and [(I 2 P 2− )(I 2 P 3− )Al] 2− show intervalence charge transfer (IVCT) transitions in the regions 6850–7740 and 7410–9780 cm −1 , respectively. Alkali metal cations in solution had no effect on the IVCT bands of [(I 2 P 2− )(I 2 P 3− )Al] 2− complexes containing –PhNMe 2 or –PhF 5 substituents. Minor localization of charge in [(I 2 P 2− )(I 2 P 3− )Al] 2− was observed when –PhOMe substituents are included. 

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2. A Contiguous Tricyclic [P ₆ ] ^2– Framework Spanning Across Two Vanadium(III) Centers

   https://doi.org/10.1021/acs.organomet.2c00638  

   Senthil, Shuruthi; Gau, Michael R.; Mindiola, Daniel J. (February 2023, Organometallics)

   Paul Chirik (Ed.)

   The complex [(BDI)VCl(N{SiMe3}2)] (1) (BDI– = [ArNC(CH3)]2CH, Ar = 2,6-iPr2C6H3), a precursor readily prepared from metathesis of [(BDI)VCl2] and Na[N{SiMe3}2], can be reduced with Na/NaCl in the presence of white P4 to form a dinuclear species containing two VIII centers bridged by a tricyclic [P6]2– scaffold, namely, [(BDI)V(N{SiMe3}2)]2(μ-η1:η1-P6) (2). Coordination of [P6]2– involves a unique chairlike μ-η1:η1 binding mode with a contiguous tricyclic hexaphosphorus unit bridging across the two V centers. Complexes 1 and 2 have been structurally characterized, and a pathway toward the formation of the chairlike tricyclic [P6]2– scaffold in 2 is proposed. 

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3. Copper‐Catalyzed C(sp ³ )−H α‐Acetylation: Generation of Quaternary Centers

   https://doi.org/10.1002/anie.202418692  

   Okoromoba, Otome_E; Chen, Ting‐An; Jang, Eun_Sil; McMullin, Claire_L; Cundari, Thomas_R; Warren, Timothy_H (November 2024, Angewandte Chemie International Edition)

   Abstract α‐substituted ketones are important chemical targets as synthetic intermediates as well as functionalities in natural products and pharmaceuticals. We report the α‐acetylation of C(sp³)−H substrates R−H with arylmethyl ketones ArC(O)Me to provide α‐alkylated ketones ArC(O)CH₂R at RT with^tBuOO^tBu as oxidant via copper(I) ‐diketiminato catalysts. Proceeding via alkyl radicals R•, this method enables α‐substitution with bulky substituents without competing elimination that occurs in more traditional alkylation reactions between enolates and alkyl electrophiles. DFT studies suggest the intermediacy of copper(II) enolates [Cu^II](CH₂C(O)Ar) that capture alkyl radicals R• to give R−CH₂C(O)Ar outcompeting dimerization of the copper(II) enolate to give the 1,4‐diketone ArC(O)CH₂CH₂C(O)Ar. 

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4. Methanesulfonyl-polarized halogen bonding enables strong halide recognition in an arylethynyl anion receptor

   https://doi.org/10.1039/c8cc09251f  

   Lohrman, Jessica A.; Deng, Chun-Lin; Shear, Trevor A.; Zakharov, Lev N.; Haley, Michael M.; Johnson, Darren W. (February 2019, Chemical Communications)

   A 3,5-bis((2-iodophenyl)ethynyl)pyridinium scaffold was synthesized which introduces the use of methanesulfonyl withdrawing groups to polarize iodine halogen bonding units for anion binding. We investigate the capability of this receptor to bind halides in polar media, while further probing the structure–property relationship of this well-polarized yet under-explored halogen bonding system. 

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5. Competition Between the Two σ‐Holes in the Formation of a Chalcogen Bond

   https://doi.org/10.1002/cphc.202200936  

   Scheiner, Steve (February 2023, ChemPhysChem)

   Abstract A chalcogen atom Y contains two separate σ‐holes when in a R₁YR₂molecular bonding pattern. Quantum chemical calculations consider competition between these two σ‐holes to engage in a chalcogen bond (ChB) with a NH₃base. R groups considered include F, Br, I, and tert‐butyl (tBu). Also examined is the situation where the Y lies within a chalcogenazole ring, where its neighbors are C and N. Both electron‐withdrawing substituents R₁and R₂act cooperatively to deepen the two σ‐holes, but the deeper of the two holes consistently lies opposite to the more electron‐withdrawing group, and is also favored to form a stronger ChB. The formation of two simultaneous ChBs in a triad requires the Y atom to act as double electron acceptor, and so anti‐cooperativity weakens each bond relative to the simple dyad. This effect is such that some of the shallower σ‐holes are unable to form a ChB at all when a base occupies the other site. 

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