Carbene mesoionic

For imidazolium salts 1, an alternative pathway with deprotonation and carbene generation at the C4/C5-position was observed previously the carbenes thus generated are called abnormal carbenes [79-81]. Likewise, suitably substituted imidazo[l,5-a]pyridinium salts can be deprotonated to mesoionic carbenes 10b and the corresponding silver, iridium and rhodium complexes were formed. 

Fig. 9 Pd l,2,3-triazol-5-ylidene mesoionic carbene PEPPSI complexes.

To conclude this section just a quick word about triazolium cation derivatives of 1,2,3-triazoles [87]. They have also been investigated and show application for functional ionic liquids and precursors of mesoionic carbenes for catalytic purposes, or as units of supramolecular assemblies and molecular machines. 

The Cu(l) complex formed by a mesoionic carbene and a phenanthroline has been generated in situ to perform copper-catalysed azide-alkyne cycloaddition in alcoholic solvent and without the need for a reducing reagent. ... 

Poly-NHC Ligands Containing Abnormal, Remote, or Mesoionic Carbenes 216... 

The statements abnormal and mesoionic carbenes (aNHCs and MICs) are synonyms and are referred to free carbenes for which it is not possible to draw a structure resonance formula without formal charges (Fig. 6). Differ-endy, remote carbenes (rNHCs) are carbenes without any heteroatom in the a and positions of the carbene center. These three types of ligands are characterized by a different structure with respect to the one usuaUy owned by NHCs. In the case of normal carbenes (nNHCs), the carbene donor is stabilized by the presence in the a and a positions of two heteroatoms. To emphasize this difference, aNHCs, MICs, and rNHCs are also caUed... 

Guisado-Barrios G, Bouf rdJ, Donnadieu B, Bertrand G. Bis(l, 2,3-triazol-5-ylidenes) (i-bitz) as stable 1,4-bidentate ligands based on mesoionic carbenes (MICs). Organometallics. 2011 30 6017-6021. 

Maity R, Hohloch S, Su C-Y, Van der Meer M, Sarkar B. Cyclometalated mono- and dinuclear Ir complexes with cHck -derived triazoles and mesoionic carbenes. Chem Eur J. 2014 20 9952-9961. 

Maity R, Van der Meet M, Sarkar B. Redox-active mrJtinuclear Pd(II) complexes with bis- and tris-mesoionic carbenes. Dalton Trans. 2015 44 46-49. 

Lee W-T, Dickie DA, Metta-Magan AJ, Smith JM. A tripodal bgand constructed from mesoionic carbene donors. Inorg Chem. 2013 52 12842-12846. 

Zamora MT, Ferguson MJ, Cowie M. Di-mesoionic carbene-bridged complexes of Rh2, It2 and Rhir a stepwise metalation strategy for the synthesis of di-MIC-bridges mixed-metal systems. Organometallics. 2012 31 5384-8395. 

Figure 1.10 Chiral triazolium salts 113-114, mesoionic carbenes 115-116 and dicationic triazolium salt 117.

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