Labile Rhodium(I)–N-Heterocyclic Carbene Complexes

Abstract

The neutral square-planar complexes Rh­(acac)­(IPr)­(η²<i>-</i>olefin) have been prepared from [Rh­(μ-Cl)­(IPr)­(η²<i>-</i>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<i>-</i>coe), [Rh­(IPr)­(η²<i>-</i>coe)­(NCCH₃)₂]­OTf, and [Rh­(IPr)­(NCCH₃)₃]­OTf complexes. The derivative [Rh­(IPr)­(η²<i>-</i>coe)­(NCCH₃)₂]­OTf was further characterized by an X-ray diffraction analysis