Labile rhodium(I)-N-heterocyclic carbene complexes

Abstract

The neutral square-planar complexes Rh(acac)(IPr)(η2-olefin) have been prepared from [Rh(μ-Cl)(IPr)(η2-olefin)]2 (IPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-carbene; olefin = cyclooctene, ethylene) and sodium acetylacetonate (acac). Protonation of the acetylacetonato complexes with triflic acid opens the way to the formation of the putative bare [Rh-IPr]+ fragment that has been stabilized at low temperature by labile ligands such as triflate, cyclooctene, and acetonitrile to generate Rh(OTf)(IPr)(η2-coe), [Rh(IPr)(η2-coe)(NCCH3)2]OTf, and [Rh(IPr)(NCCH3)3]OTf complexes. The derivative [Rh(IPr)(η2-coe)(NCCH3)2]OTf was further characterized by an X-ray diffraction analysis.