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1. Metalated isocyanides: formation, structure, and reactivity

   https://doi.org/10.1039/D0OB01340D  

   Altundas, Bilal; Marrazzo, John-Paul R.; Fleming, Fraser F. (August 2020, Organic & Biomolecular Chemistry)

   null (Ed.)

   Metalated isocyanides are highly versatile organometallics. Central to the reactivity of metalated isocyanides is the presence of two orthogonally reactive carbons, a highly nucleophilic “carbanion” inductively stabilized by a carbene-like isocyanide carbon. The two reactivities are harnessed in the attack of metalated isocyanides on π-electrophiles where an initial nucleophilic attack leads to an electron pair that cyclizes onto the terminal isocyanide carbon in a rapid route to diverse, nitrogenous heterocycles. Harnessing the potent nucleophilicity of metalated isocyanides while preventing electrophilic attack on the terminal isocyanide carbon has largely been driven by empirical heuristics. This review provides a foundational understanding by surveying the formation, structure, and properties of metalated isocyanides. The focus on the interplay between the structure and reactivity of metalated isocyanides is anticipated to facilitate the development and deployment of these exceptional nucleophiles in complex bond constructions. 

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2. Bypassing the Nitrido Wall Using a Redox‐Active Isocyanide: Nucleophilic Attack on CO by a Rhenium Nitride Complex

   https://doi.org/10.1002/anie.202504245  

   Hegg, Alexander_S; Donnelly, Ryan_S; Weber, Jeremy_E; Crabtree, Robert_H; Mercado, Brandon_Q; Holland, Patrick_L (June 2025, Angewandte Chemie International Edition)

   Abstract Reactive rhenium(III) nitride complexes could result from filling Re─N π* orbitals, but such complexes lie beyond the “nitrido wall” and are rare due to their instability. Here, we describe a method for bypassing the nitrido wall by incorporating a redox‐active isocyanide supporting ligand, which accommodates two electrons as shown by crystallographic, spectroscopic, and computational studies. These electrons can be returned to the metal during its facile reaction with CO to form a cyanate complex, demonstrating the nucleophilic reactivity of the nitride. Thus, assistance by the isocyanide enables an N₂‐derived rhenium nitride to engage in N─C bond forming reactivity. 

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3. Rate Dependence on Inductive and Resonance Effects for the Organocatalyzed Enantioselective Conjugate Addition of Alkenyl and Alkynyl Boronic Acids to β-Indolyl Enones and β-Pyrrolyl Enones

   https://doi.org/10.3390/molecules26061615  

   Boylan, Amy; Nguyen, Thien S.; Lundy, Brian J.; Li, Jian-Yuan; Vallakati, Ravikrishna; Sundstrom, Sasha; May, Jeremy A. (March 2021, Molecules)

   null (Ed.)

   Two key factors bear on reaction rates for the conjugate addition of alkenyl boronic acids to heteroaryl-appended enones: the proximity of inductively electron-withdrawing heteroatoms to the site of bond formation and the resonance contribution of available heteroatom lone pairs to stabilize the developing positive charge at the enone β-position. For the former, the closer the heteroatom is to the enone β-carbon, the faster the reaction. For the latter, greater resonance stabilization of the benzylic cationic charge accelerates the reaction. Thus, reaction rates are increased by the closer proximity of inductive electron-withdrawing elements, but if resonance effects are involved, then increased rates are observed with electron-donating ability. Evidence for these trends in isomeric substrates is presented, and the application of these insights has allowed for reaction conditions that provide improved reactivity with previously problematic substrates. 

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4. Metalloradical Catalysis: General Approach for Controlling Reactivity and Selectivity of Homolytic Radical Reactions

   https://doi.org/10.1002/anie.202320243  

   Lee, Wan‐Chen Cindy; Zhang, X. Peter (April 2024, Angewandte Chemie International Edition)

   Abstract Since Friedrich Wöhler's groundbreaking synthesis of urea in 1828, organic synthesis over the past two centuries has predominantly relied on the exploration and utilization of chemical reactions rooted in two‐electron heterolytic ionic chemistry. While one‐electron homolytic radical chemistry is both rich in fundamental reactivities and attractive with practical advantages, the synthetic application of radical reactions has been long hampered by the formidable challenges associated with the control over reactivity and selectivity of high‐energy radical intermediates. To fully harness the untapped potential of radical chemistry for organic synthesis, there is a pressing need to formulate radically different concepts and broadly applicable strategies to address these outstanding issues. In pursuit of this objective, researchers have been actively developing metalloradical catalysis (MRC) as a comprehensive framework to guide the design of general approaches for controlling over reactivity and stereoselectivity of homolytic radical reactions. Essentially, MRC exploits the metal‐centered radicals present in open‐shell metal complexes as one‐electron catalysts for homolytic activation of substrates to generate metal‐entangled organic radicals as the key intermediates to govern the reaction pathway and stereochemical course of subsequent catalytic radical processes. Different from the conventional two‐electron catalysis by transition metal complexes, MRC operates through one‐electron chemistry utilizing stepwise radical mechanisms. 

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5. η2 Coordination of Electron-Deficient Arenes with Group 6 Dearomatization Agents

   https://doi.org/10.1021/acs.organomet.0c00277  

   Smith, J. A.; Simpson, S. R.; Westendorff, K. S.; Weatherford-Pratt, J.; Myers, J. T.; Wilde, J. H.; Dickie, D. A.; Harman, W. D. (June 2020, Organometallics)

   null (Ed.)

   The exceptionally π-basic metal fragments {MoTp(NO)(DMAP)} and {WTp(NO)(PMe3)} (Tp = tris(pyrazolyl)borate; DMAP = 4-(N,N-dimethylamino)pyridine) form thermally stable η2-coordinated complexes with a variety of electron-deficient arenes. The tolerance of substituted arenes with fluorine-containing electron withdrawing groups (EWG; −F, −CF3, −SF5) is examined for both the molybdenum and tungsten systems. When the EWG contains a π bond (nitriles, aldehydes, ketones, ester), η2 coordination occurs predominantly on the nonaromatic functional group. However, complexation of the tungsten complex with trimethyl orthobenzoate (PhC(OMe)3) followed by hydrolysis allows access to an η2-coordinated arene with an ester substituent. In general, the tungsten system tolerates sulfur-based withdrawing groups well (e.g., PhSO2Ph, MeSO2Ph), and the integration of multiple electron-withdrawing groups on a benzene ring further enhances the π-back-bonding interaction between the metal and aromatic ligand. While the molybdenum system did not form stable η2-arene complexes with the sulfones or ortho esters, it was capable of forming rare examples of stable η2-coordinated arene complexes with a range of fluorinated benzenes (e.g., fluorobenzene, difluorobenzenes). In contrast to what has been observed for the tungsten system, these complexes formed without interference of C–H or C–F insertion. 

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