Density Functional Theory Investigation of the Alkyl-Alkyl Negishi Cross-Coupling Reaction Catalyzed by N-Heterocyclic Carbene (NHC)-Pd Complexes

作者：Chass Gregory A^*; O'Brien Christopher J; Hadei Niloufar; Kantchev Eric Assen B; Mu Wei Hua; Fang De Cai; Hopkinson Alan C; Csizmadia Imre G; Organ Michael G

来源：Chemistry - A European Journal, 2009, 15(17): 4281-4288.

DOI：10.1002/chem.200900042

• cross-coupling
• density functional calculations
• N-heterocyclic carbenes
• palladium
• zinc

A novel mechanism is proposed for the Pd-1,3-(2,6-diisopropylphenyl)imidazolyl-2-ylidene (1) catalyzed Negishi reaction. DFT computations supported by atoms-in-molecules (AIM) analyses of non-truncated models show that a "steric wait" created by the N-substituent on the ligand guides reactants to and from the Pd center. Notably, transmetalation and not oxidative addition is found to be rate-limiting. Additionally, a key Pd-Zn interaction (approximate to 2.4 angstrom, rho(b) approximate to 0.0600 au) is identified in the mechanism. This interaction persists beyond reductive elimination and, in combination with the ligand, facilitates reductive elimination by creating a highly sterically crowded environment in the coordination sphere of the Pd center.

• 出版日期2009
• 单位北京师范大学