Structure and Reactivity of "Unusual" N-Heterocyclic Carbene (NHC) Palladium Complexes Synthesized from Imidazolium Salts

Journal of the American Chemical Society

Volumn 126, Issue 16, 2004, Pages 5046-5047

  Lebel, Hélène ^a   Janes, Marc K ^a   Charette, André B ^a   Nolan, Steven P ^b  

^a UNIVERSITÉ DE MONTRÉAL   (Canada)

^b UNIVERSITY OF NEW ORLEANS   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

CARBENOID; IMIDAZOLE DERIVATIVE; PALLADIUM COMPLEX;

ARTICLE; CARBON NUCLEAR MAGNETIC RESONANCE; CRYSTAL STRUCTURE; HECK REACTION; NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY; PROTON NUCLEAR MAGNETIC RESONANCE; REACTION ANALYSIS; STRUCTURE ANALYSIS; SUZUKI REACTION; SYNTHESIS; X RAY CRYSTALLOGRAPHY;

EID: 1942456891     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja049759r     Document Type: Article

References (30)

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27. The related unusual C(2)-C(5) complex was also obtained with N,N′-bis(2,6-diisopropylphenyl)imidazolium chloride (IPr·HCl).
28. 2 were obtained as an inseparable mixture.
29. The mechanism for the formation of complex 2 has not been unambiguously established. However, there are some indications that it proceeds via the formation of a palladium-carbene complex that undergo a C-H insertion into the C(5)-H bond of the second imidazolium salt. For instance, the use of weaker base, such as dimethylaniline, led mainly to formation of complex 2. Conversely, complex 2 could not be obtained from palladium chloride, which suggest that palladium acetate acted as a base for the formation of the carbene ligand. We thank a reviewer for useful comments and suggestions regarding the mechanism for the formation of 2.
30. It should be noted that in Suzuki-Miyaura cross-coupling reactions, well-defined complexes bearing only one NHC are better catalysts than those bearing two. See ref 3f.