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Cu(I) complexes of monodentate and pincer-type NHC:synthesis,characterization,and application in cross-coupling reaction

Cu(I) complexes of monodentate and pincer-type NHC:synthesis,characterization,and  application in cross-coupling reaction

Name:
Doaa Domyati

Department:
Chemistry

Abstract:
We describe the synthesis of three new Cu(I) complexes with pincer N-heterocyclic carbene (NHC) ligands bearing methylpyridine 2,6-bis(3-alkylimidazol-2-ylidene)methylpyridine, I(R)CᴖNᴖC (where R = Me, Et and iPr ) as linkers between the two NHC moieties. All of these compounds, namely [Cu(IMeCᴖNᴖC)](PF6), 1; [Cu(IEtCᴖNᴖC)](PF6), 2; and [Cu(IiPrCᴖNᴖC)](PF6), 3 have been characterized by 1H- and 13C NMR spectroscopies, elemental analysis, and single crystal X-ray structures. We have also synthesized some cationic and neutral Cu-NHC complexes, [Cu(IiPr)2]PF6 and [Cu(SIMes)Cl], respectively, and characterized them by elemental analysis and NMR spectroscopy. The two classes of Cu-NHC complexes were utilized as catalyst in the C-C bond formation between sp- and sp2-hybridized carbon atoms (Sonogashira reaction). Sonogashira coupling has been widely used in pharmaceutical, natural products, and organic syntheses and traditionally relies on Pd as the major catalyst. We have shown that some of the Cu-NHC prepared in this study such as [Cu(SIMes)Cl] can provide the cross-coupled products with the isolated yield at 65% in the absence of precious metals.