Date: September 27, 2006
Creator: Goj, Laurel A.; Blue, Elizabeth D.; Delp, Samuel A.; Gunnoe, T. Brent; Cundari, Thomas R., 1964-; Pierpont, Aaron W. et al
Description: This article discusses transition metal systems. Abstract: Monomeric copper(l) alkyl complexes that possess the N-heterocyclic carbene (NHC) ligands IPr, SIPr, and IMes [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, SIPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene, IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene] react with amines or alcohols to release alkane and form the corresponding monomeric copper(l) amido, alkoxide, or aryloxide complexes. Thermal decomposition reactions of (NHC)Cu׀ methyl complexes at temperatures between 100 and 130 °C produce methane, ethane, and ethylene. The reactions of (NHC)Cu(NHPh) complexes with bromoethane reveal increasing nucleophilic reactivity at the anilido ligand in the order (SIPR)Cu(NHPh) < (IPr)Cu(NHPh) < (IMes)Cu(NHPh) < (dtbpe)Cu(NHPh) [dtbpe = 1,2-bis(di-tert-butylphosphino)ethane]. DFT calculations suggest that the HOMO for the series of Cu anilido complexes is localized primarily on the amido nitrogen with some pπanilido-dπCu π*-character. [(IPr)Cu(μ-H)]2 and (IPr)Cu(Ph) react with aniline to quantitatively produce (IPr)Cu(NHPh)/dihydrogen and (IPr)Cu(NHPh)/benzene, respectively. Analysis of the DFT calculations reveals that the conversion of [(IPr)Cu(μ-H)]2 and aniline to (IPr)Cu(NHPh) and dihydrogen is favorable with ∆H ≈ -7 kcal/mol and ∆G ≈ -9 kcal/mol.
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