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1. Dynamic π-Bonding of Imidazolyl Substituent in a Formally 16-Electron Cp*Ru(κ ² - P , N ) ⁺ Catalyst Allows Dramatic Rate Increases in ( E )-Selective Monoisomerization of Alkenes

   https://doi.org/10.1021/acscatal.8b04345  

   Paulson, Erik R. ; Moore, Curtis E. ; Rheingold, Arnold L. ; Pullman, David P. ; Sindewald, Ryan W. ; Cooksy, Andrew L. ; Grotjahn, Douglas B. ( June 2019 , ACS Catalysis)
2. Iron-catalyzed C(sp ² )–C(sp ³ ) cross-coupling at low catalyst loading

   https://doi.org/10.1039/C8CY02374C  

   Bisz, Elwira ; Kardela, Marlena ; Piontek, Aleksandra ; Szostak, Michal ( March 2019 , Catalysis Science & Technology)

   The iron-catalyzed C(sp 2 )–C(sp 3 ) cross-coupling provides a highly economical route to exceedingly valuable alkylated arenes that are widespread in medicinal chemistry and materials science. Herein, we report an operationally-simple protocol for the selective C(sp 2 )–C(sp 3 ) iron-catalyzed cross-coupling of aryl chlorides with Grignard reagents at low catalyst loading. A broad range of electronically-varied aryl and heteroaryl chlorides underwent the cross-coupling using challenging alkyl organometallics possessing β-hydrogens with high efficiency up to 2000 TON. A notable feature of the protocol is the use of environmentally-friendly cyclic urea ligands. A series of guidelines to predict cross-coupling reactivity of aryl electrophiles is provided.
3. Reaction Mechanism Underlying Pd(II)-Catalyzed Oxidative Coupling of Ethylene and Benzene to Form Styrene: Identification of a Cyclic Mono-Pd ^II Bis-Cu ^II Complex as the Active Catalyst

   https://doi.org/10.1021/acs.organomet.2c00183  

   Musgrave, Charles B. ; Bennett, Marc T. ; Ellena, Jeffrey F. ; Dickie, Diane A. ; Gunnoe, T. Brent ; Goddard, William A. ( July 2022 , Organometallics)

   A recent advance in the synthesis of alkenylated arenes was the demonstration that the Pd(OAc)2 catalyst precursor gives >95% selectivity toward styrene from ethylene and benzene under optimized conditions using excess Cu(II) carboxylate as the in situ oxidant [ Organometallics 2019, 38(19), 3532−3541]. To understand the mechanism underlying this catalysis, we applied density functional theory (DFT) calculations in combination with experimental studies. From DFT calculations, we determined the lowest-energy multimetallic Pd and Pd–Cu mixed metal species as possible catalyst precursors. From the various structures, we determined the cyclic heterotrinuclear complex PdCu2(μ-OAc)6 to be the global minimum in Gibbs free energy under conditions of excess Cu(II). For cyclic PdCu2(μ-OAc)6 and the parent [Pd(μ-OAc)2]3, we evaluated the barriers for benzene C–H activation through concerted metalation deprotonation (CMD). The PdCu2(μ-OAc)6 cyclic trimer leads to a CMD barrier of 33.5 kcal/mol, while the [Pd(μ-OAc)2]3 species leads to a larger CMD barrier at >35 kcal/mol. This decrease in the CMD barrier arises from the insertion of Cu(II) into the trimetallic species. Because cyclic PdCu2(μ-OAc)6 is likely the predominant species under experimental conditions (the Cu to Pd ratio is 480:1 at the start of catalysis) with a predicted CMD barrier within the range of the experimentallymore »determined activation barrier, we propose that cyclic PdCu2(μ-OAc)6 is the Pd species responsible for catalysis and report a full reaction mechanism based on DFT calculations. For catalytic conversion of benzene and ethylene to styrene at 120 °C using Pd(OAc)2 as the catalyst precursor and Cu(OPiv)2 (OPiv = pivalate) as the oxidant, an induction period of ∼1 h was observed, followed by catalysis with a turnover frequency of ∼2.3 × 10–3 s–1. In situ1H NMR spectroscopy experiments indicate that during the induction period, Pd(OAc)2 is likely converted to cyclic PdCu2(η2-C2H4)3(μ-OPiv)6, which is consistent with the calculations and consistent with the proposal that the active catalyst is the ethylene-coordinated heterotrinuclear complex cyclic PdCu2(η2-C2H4)3(μ-OPiv)6.« less
4. Iron‐Catalyzed C( sp ² )−C( sp ³ ) Cross‐Coupling of Chlorobenzamides with Alkyl Grignard Reagents: Development of Catalyst System, Synthetic Scope, and Application

   https://doi.org/10.1002/adsc.201800849  

   Bisz, Elwira ; Szostak, Michal ( November 2018 , Advanced Synthesis & Catalysis)
5. A General Protocol for Addressing Speciation of the Active Catalyst Applied to Ligand-Accelerated Enantioselective C(sp ³ )–H Bond Arylation

   https://doi.org/10.1021/acscatal.8b00103  

   Hill, David E. ; Pei, Qing-lan ; Zhang, En-xuan ; Gage, James R. ; Yu, Jin-Quan ; Blackmond, Donna G. ( January 2018 , ACS Catalysis)