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1. L‐Shaped Heterobidentate Imidazo[1,5‐ a ]pyridin‐3‐ylidene (N,C)‐Ligands for Oxidant‐Free Au ^I /Au ^III Catalysis

   https://doi.org/10.1002/ange.202218427  

   Gao, Pengcheng; Xu, Jihong; Zhou, Tongliang; Liu, Yanhong; Bisz, Elwira; Dziuk, Błażej; Lalancette, Roger; Szostak, Roman; Zhang, Dongju; Szostak, Michal (March 2023, Angewandte Chemie)
2. Well-defined, air- and moisture-stable palladium–imidazo[1,5- a ]pyridin-3-ylidene complexes: a versatile catalyst platform for cross-coupling reactions by L-shaped NHC ligands

   https://doi.org/10.1039/D2CY01136K  

   Zhou, Tongliang; Gao, Pengcheng; Bisz, Elwira; Dziuk, Błażej; Lalancette, Roger; Szostak, Roman; Szostak, Michal (October 2022, Catalysis Science & Technology)

   We describe the development of [(NHC)Pd(cinnamyl)Cl] complexes of ImPy (ImPy = imidazo[1,5- a ]pyridin-3-ylidene) as a versatile class of precatalysts for cross-coupling reactions. These precatalysts feature fast activation to monoligated Pd(0) with 1 : 1 Pd to ligand ratio in a rigid imidazo[1,5- a ]pyridin-3-ylidene template. Steric matching of the C5-substituent and N2-wingtip in the catalytic pocket of the catalyst framework led to the discovery of ImPyMesDipp as a highly reactive imidazo[1,5- a ]pyridin-3-ylidene ligand for Pd-catalyzed cross-coupling of nitroarenes by challenging C–NO 2 activation. Kinetic studies demonstrate fast activation and high reactivity of this class of well-defined ImPy–Pd catalysts. Structural studies provide full characteristics of this new class of imidazo[1,5- a ]pyridin-3-ylidene ligands. Computational studies establish electronic properties of sterically-restricted imidazo[1,5- a ]pyridin-3-ylidene ligands. Finally, a scalable synthesis of C5-substituted imidazo[1,5- a ]pyridin-3-ylidene ligands through Ni-catalyzed Kumada cross-coupling is disclosed. The method obviates chromatographic purification at any of the steps, resulting in a facile and modular access to ImPy ligands. We anticipate that well-defined [Pd–ImPy] complexes will find broad utility in organic synthesis and catalysis for activation of unreactive bonds. 

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3. Polymorphism in 9-[(9 H -Fluoren-9-ylidene)methyl]phenanthrene

   https://doi.org/10.1021/acs.cgd.2c00120  

   Roth, Alexander D.; Thamattoor, Dasan M. (August 2022, Crystal Growth & Design)
4. Combining Donor Strength and Oxidative Stability in Scorpionates: A Strongly Donating Fluorinated Mesoionic Tris(imidazol-5-ylidene)borate Ligand

   https://doi.org/10.1021/acs.inorgchem.3c03251  

   Scott, Joseph S; Schneider, Joseph E; Tewelde, Eyob G; Gardner, Joel G; Anferov, Sophie W; Filatov, Alexander S; Anderson, John S (December 2023, Inorganic Chemistry)
5. Crystal structures of (η ⁴ -cycloocta-1,5-diene)bis(1,3-dimethylimidazol-2-ylidene)iridium(I) iodide and (η ⁴ -cycloocta-1,5-diene)bis(1,3-diethylimidazol-2-ylidene)iridium(I) iodide

   https://doi.org/10.1107/S2056989020004235  

   Bernier, Chad M.; DuChane, Christine M.; Merola, Joseph S. (May 2020, Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   The title complexes, (η 4 -cycloocta-1,5-diene)bis(1,3-dimethylimidazol-2-ylidene)iridium(I) iodide, [Ir(C 5 H 8 N 2 ) 2 (C 8 H 12 )]I, ( 1 ) and (η 4 -cycloocta-1,5-diene)bis(1,3-diethylimidazol-2-ylidene)iridium(I) iodide, [Ir(C 7 H 12 N 2 ) 2 (C 8 H 12 )]I, ( 2 ), were prepared using a modified literature method. After carrying out the oxidative addition of the amino acid L-proline to [Ir(COD)(IMe) 2 ]I in water and slowly cooling the reaction to room temperature, a suitable crystal of 1 was obtained and analyzed by single-crystal X-ray diffraction at 100 K. Although this crystal structure has previously been reported in the Pbam space group, it was highly disordered and precise atomic coordinates were not calculated. A single crystal of 2 was also obtained by heating the complex in water and letting it slowly cool to room temperature. Complex 1 was found to crystallize in the monoclinic space group C 2/ m , while 2 crystallizes in the orthorhombic space group Pccn , both with Z = 4. 

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