The tendency of carbenes to bind more strongly to metal-centres compared to nitrogen- or phosphorous-based ligands, and the robust nature of the corresponding complexes, render the search for new stable carbenes as highly desirable due to the wide number of potential applications.Recently, the preparation of free triazolylidenes (mesoioniccarbenes MICs) has been reported, exhibiting greater donor properties than those of NHCs.[1] In addition, MICs have also proven to be competent ligands for transition metal-catalysis. Another class of carbenes prepared by the group of Bertrand[2] is the cyclic(alkyl)aminocarbenes (CAACs), which exhibit unique donating/accepting properties.

New N,N’-diarylated 1H-1,2,3-triazol-5-ylidene amido pincer ligands, or bisMIC-amido pincer ligands, have been designed, as pincer-type ligands are widely known to form robust metal complexes due to the chelating effect. This has been demonstrated by the isolation of reactive species, such as metal hydride complexes, and has contributed to their application in catalysis.[3] The synthesis of these ligands, as well as their complexation with transition metals are presented here. In addition, the formation of low valent 14-electron complexes bearing CAAC-ligands are reported, and the study of their reactivity for application in catalytic processes such as hydroamination and hydrogenation.

[1]           G. Guisado-Barrios, J. Bouffard, B. Donnadieu, G. Bertrand, Angew. Chem. Int. Ed., 2010, 49, 4759.
[2]           V. Lavallo, Y. Canac, C. Prasang, B. Donnadieu, G. Bertrand, Angew. Chem. Int. Ed., 2005, 44, 5075.
[3]           M. Poyatos, J.A. Mata, E. Peris, Chem. Rev. 2009, 109, 3677. [3] D. Pugh, A. Boyle, A.A. Danopoulos, Dalton Trans. 2008, 1087. [4] J. Breitenfeld, R. Scopelliti, X. Hu, Organometallics 2012, 31, 2128.