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 [(eta(5)-C5Me5)MCl2](2) (M=Rh, Ir) afforded the rhodium(III) and iridium(III) half-sandwich complexes [{(WCA-IDipp)E}MCl(eta(5)-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 [mu(2)-{(WCA-IDipp)E}M-2(COD)(2)(mu(2)-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 pi-interaction.