| 19397262 |
Galan BR, Pitak M, Gembicky M, Keister JB, Diver ST: Ligand-promoted carbene insertion into the aryl substituent of an N-heterocyclic carbene ligand in ruthenium-based metathesis catalysts. J Am Chem Soc. 2009 May 20;131(19):6822-32.
Addition of L = carbon monoxide or aryl isocyanides to the Grubbs second-generation carbene complexes Ru (H (2) IMes)(CHR)(PCy (3)) Cl (2) (H (2) IMes = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene; R = Ph, Me, H, CH=CMe (2)) triggers carbene insertion into an aromatic ring of the N-heterocyclic carbene supporting ligand, forming Ru{1-mesityl-3-(-7'-R-2',4',6'-trimethylcycloheptatrienyl)-4,5-dihydroimid azol-2-ylidene}L (2)(PCy (3)) Cl (2). Insertions are also promoted for other PR (3) substituted complexes by carbon monoxide and aryl isocyanides, and for the phosphine-free Hoveyda-Blechert complex Ru (H (2) IMes)(CH (i-PrOC (6) H (4))) Cl (2) by aryl isocyanides and small phosphites but only after initial displacement of the coordinated ether. Heteroatom substituted carbenes do not undergo CO-promoted insertion unless poorer electron donor phosphine (PPh (3)) and carbene (CH (OC (6) H (4)-p-NO (2)) ligands are both present. Insertion depends on the added ligand, the carbene substituent, and to a lesser degree on the PR (3) ligand trans to the N-heterocyclic carbene. |
82(1,1,1,2) |