Direct C-metallation of N-substituted triazoles promoted by mercury acetate. An alternative route to N-heterocyclic carbene complexes

C-Metallation of neutral mono-substituted triazoles could be induced by Hg(OAc)2 to give a near quantitative yield of C,N-bonded mercury complexes. Initial N-coordination to mercury(II) is confirmed by NMR spectroscopy. Subsequent acetate assisted deprotonation–metallation is a viable route to C-metallated products. Hg(OAc)2 is unique for this reaction. Metal salts of Ag2O, Ag(OAc), Pd(OAc)2 or HgCl2 in combination with bases of NaOH and K2CO3 did not yield triazolate complexes. Further reaction of one of these mercury(II)–C,N-triazolate complexes with a source of methyl cation yielded a monomeric N-heterocyclic carbene complex. Therefore the facile reaction of triazole with Hg(OAc)2 followed by alkylation is a handy alternative way to prepare Hg–NHCs.

[1]  M. Ferguson,et al.  N‐Heterocyclic Carbene Reactivity Towards Mercurous Chloride , 2016 .

[2]  Gene-Hsiang Lee,et al.  Formation of NH,NR N‐Heterocyclic Carbene Complexes through Mercuration of Mono‐N‐substituted Benzimidazoles , 2016 .

[3]  T Gensch,et al.  Mild metal-catalyzed C-H activation: examples and concepts. , 2016, Chemical Society reviews.

[4]  F. Hahn,et al.  Complexes with protic (NH,NH and NH,NR) N-heterocyclic carbene ligands , 2015 .

[5]  F. Hahn,et al.  Complexes Bearing Protic N-Heterocyclic Carbenes: Synthesis and Applications , 2015 .

[6]  T. Ikariya,et al.  Metal-ligand bifunctional reactivity and catalysis of protic N-heterocyclic carbene and pyrazole complexes featuring β-NH units. , 2014, Chemical communications.

[7]  B. Cossairt,et al.  Mono- and Dimetalation of a Tridentate Bisimidazole-Phosphine Ligand , 2014 .

[8]  C. Schulte to Brinke,et al.  A versatile methodology for the regioselective C⁸-metalation of purine bases. , 2014, Journal of the American Chemical Society.

[9]  F. Hahn,et al.  Oxidative addition of 2-halogenoazoles-direct synthesis of palladium(II) complexes bearing protic NH,NH-functionalized NHC ligands. , 2014, Angewandte Chemie.

[10]  Qing-Shan Li,et al.  Mono- and dinuclear Hg(II) complexes of bis-(N-heterocyclic carbene) bridged with calixarene fragments: Synthesis, structure and sensing behavior , 2014 .

[11]  Srinivasa Budagumpi,et al.  Group XII Metal–N-Heterocyclic Carbene Complexes: Synthesis, Structural Diversity, Intramolecular Interactions, and Applications , 2013 .

[12]  F. Hahn.  Substrate Recognition and Regioselective Catalysis with Complexes Bearing NR,NH‐NHC Ligands , 2013 .

[13]  F. Lahoz,et al.  Synthesis of complexes containing an anionic NHC ligand with an unsubstituted ring-nitrogen atom. , 2012, Chemistry.

[14]  Junhua Li,et al.  A highly efficient Cu-catalyst system for N-arylation of azoles in water , 2012 .

[15]  F. Hahn,et al.  Synthesis of Rhodium(I) Complexes Bearing Bidentate NH,NR-NHC/Phosphine Ligands , 2011 .

[16]  R. López,et al.  Imidazole to NHC rearrangements at molybdenum centers: an experimental and theoretical study. , 2011, Chemistry.

[17]  F. Hahn,et al.  Synthesis of NHC complexes by oxidative addition of 2-chloro-N-methylbenzimidazole. , 2011, Journal of the American Chemical Society.

[18]  S. Pelz,et al.  “Oxide Route” for the Preparation of Mercury(II) N-Heterocyclic Carbene Complexes , 2011 .

[19]  S. García‐Granda,et al.  On the existence of an N-Metalated N-Heterocyclic carbene: A theoretical study , 2010 .

[20]  R. López,et al.  From bis(N-alkylimidazole) to bis(NH-NHC) in rhenium carbonyl complexes. , 2010, Angewandte Chemie.

[21]  R. Crabtree,et al.  Acyl Protection Strategy for Synthesis of a Protic NHC Complex via N-Acyl Methanolysis† , 2010 .

[22]  B. Skelton,et al.  Mercury Complexes of N-Heterocyclic Carbenes Derived from Imidazolium-Linked Cyclophanes: Synthesis, Structure, and Reactivity , 2009 .

[23]  Julio Pérez,et al.  From N-alkylimidazole ligands at a rhenium center: ring opening or formation of NHC complexes. , 2008, Journal of the American Chemical Society.

[24]  A. Rheingold,et al.  Imidazol-2-yl complexes of Cp*Ir as bifunctional ambident reactants. , 2008, Journal of the American Chemical Society.

[25]  T. Ikariya,et al.  Isolation and Interconversion of Protic N-Heterocyclic Carbene and Imidazolyl Complexes: Application to Catalytic Dehydrative Condensation of N-(2-Pyridyl)benzimidazole and Allyl Alcohol , 2008 .

[26]  F. Hahn,et al.  Heterocyclic carbenes: synthesis and coordination chemistry. , 2008, Angewandte Chemie.

[27]  G. Sheldrick.  A short history of SHELX. , 2008, Acta crystallographica. Section A, Foundations of crystallography.

[28]  Gaocan Li,et al.  Simple copper salt-catalyzed N-arylation of nitrogen-containing heterocycles with aryl and heteroaryl halides. , 2007, The Journal of organic chemistry.

[29]  J. Ruiz,et al.  Base-promoted tautomerization of imidazole ligands to N-heterocyclic carbenes and subsequent transmetalation reaction. , 2007, Journal of the American Chemical Society.

[30]  S. Waldvogel,et al.  Molecular recognition utilizing complexes with NH,NR-stabilized carbene ligands , 2007 .

[31]  M. Whittlesey,et al.  Ruthenium induced C-N bond activation of an N-heterocyclic carbene: isolation of C- and N-bound tautomers. , 2006, Journal of the American Chemical Society.

[32]  J. Ellman,et al.  Arylation of heterocycles via rhodium-catalyzed C-H bond functionalization. , 2004, Organic letters.

[33]  O. Guerret,et al.  Synthesis and structure of 1,2,4-triazol-2-ium-5-ylidene complexes of Hg(II), Pd(II), Ni(II), Ni(0), Rh(I) and Ir(I) , 2002 .

[34]  K. Tan,et al.  Intermediacy of an N-heterocyclic carbene complex in the catalytic C-H activation of a substituted benzimidazole. , 2002, Journal of the American Chemical Society.

[35]  R. Crabtree,et al.  Preferential C-binding versus N-binding in imidazole depends on the metal fragment involved. , 2002, Inorganic chemistry.

[36]  H. Raubenheimer,et al.  Carbene complexes derived from lithiated heterocycles, mainly azoles, by transmetallation. , 2001 .

[37]  I. J. Lin,et al.  The first dicarbene double helical mercury complex , 2000 .

[38]  B. Bovio,et al.  Reactions of C-imidazolyllithium derivatives with Group Ib compounds: Tris[μ-(1-alkylimidazolato-N3,C2)]tri-gold(I) and -silver(I). Crystal structure of bis(1-benzylimidazolin-2-yliden)gold(I) chloride , 1989 .

[39]  R. Sundberg,et al.  Nitrogen-bound and carbon-bound imidazole complexes of ruthenium ammines , 1974 .

[40]  L. Fusina,et al.  Infrared and Raman spectra of addition compounds of sulphoxides with mercury(II) chloride , 1972 .