New Rhodium(I) Carbene Complexes from Carbene Transfer Reactions

The Rh(I) complexes RhCl(diene)(NHC) have been synthesized from Ag(I) carbene precursors, where NHC is one of the N-heterocyclic carbenes 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr), 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), 3-methyl-1-phenacylimidazol-2-ylidene (MAI), and 3-methyl-1-picolylimidazol-2-ylidene (MPI), and diene is either NBD or COD. The complexes are characterized by elemental analysis, ¹H NMR and IR spectroscopies, mass spectrometry, and, in the case of RhCl(NBD)(IMes) and RhCl(COD)(MAI), X-ray crystallography. The new Ag(I) carbene complexes [Ag(IPr)₂]PF₆ and [Ag(IMes)₂]PF₆ are also reported.