On the involvement of NHC carbenes in catalytic reactions by iridium complexes, nanoparticle and bulk metal dispersed in imidazolium ionic liquids.
D/H exchange reactions at C2, C4 and C5 of the imidazolium cation were observed in catalytic hydrogenation reactions promoted by classical Ir(I) colloid precursors and [Ir(0)](n) nanoparticles dispersed in deuterated imidazolium ionic liquids indicating the participation of carbene species in this media. However, no D/H exchange reaction was observed in cyclohexene hydrogenation promoted by iridium bulk metal dispersed in the ionic liquid [BMI]-d(3).NTf(2). The D/H labeling experiments suggest that the ionic liquids interact with the metal centers preferentially as aggregates rather than isolated ions.
Laboratory of Molecular Catalysis, Institute of Chemistry--UFRGS, Avenida Bento Gonçalves, 9500 P.O. Box 15003, 91501-970, Porto Alegre, RS Brazil.
Jackson D
JD
Scholten
Günter
G
Ebeling
Jairton
J
Dupont