Rhodium and Iridium Complexes of Anionic Thione and Selone Ligands Derived from Anionic N-Heterocyclic Carbenes

The lithium salts of anionic N-heterocyclic thiones and selones [{(WCA-IDipp)E}Li(toluene)] ( 1 : E=S; 2 : E=Se; WCA=B(C₆F₅)₃, IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene), which contain a weakly coordinating anionic (WCA) borate moiety in the imidazole backbone were reacted with Me₃SiCl, to furnish the silylated adducts (WCA-IDipp)ESiMe₃ ( 3 : E=S; 4 : E=Se). The reaction of the latter with [(η⁵-C₅Me₅)MCl₂]₂ (M=Rh, Ir) afforded the rhodium(III) and iridium(III) half-sandwich complexes [{(WCA-IDipp)E}MCl(η⁵-C₅Me₅)] ( 5 – 8 ). The direct reaction of the lithium salts 1 and 2 with a half or a full equivalent of [M(COD)Cl]₂ (M=Rh, Ir) afforded the monometallic complexes [{(WCA-IDipp)E}M(COD)] ( 9 – 12 ) or the bimetallic complexes [μ₂-{(WCA-IDipp)E}M₂(COD)₂(μ₂-Cl)] ( 13 – 16 ), respectively. The bonding situation in these complexes has been investigated by means of density functional theory (DFT) calculations, revealing thiolate or selenolate ligand character with negligible metal-chalcogen π-interaction.