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

Abstract

The lithium salts of anionic N-heterocyclic thiones and selones [{(WCA-IDipp)E}Li(toluene)] (1: E = S; 2: E = Se; WCA = B(C 6 F 5 ) 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 Me 3 SiCl, to furnish the silylated adducts (WCA-IDipp)ESiMe 3 (3: E = S; 4: E = Se). The reaction of the latter with [(η 5 -C 5 Me 5 )MCl 2 ] 2 (M = Rh, Ir) afforded the rhodium(III) and iridium(III) half-sandwich complexes [{(WCA-IDipp)E} MCl(η 5 -C 5 Me 5 )] (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 [μ 2 -{(WCA-IDipp)E}M 2 (COD) 2 (μ 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 metalchalcogen π-interaction.

Synthesis and Reversible H2 Activation by Coordinatively Unsaturated Rhodium NHC Complexes

“…[27 -31] Among the reported (NHC)Rh(I)(COD) and (NHC)Ir(I)(COD) complexes bearing a cationic metal center, a second dative interaction from the NHC ligand in addition to the carbene coordination leads to a metal with a formal 16 e À configuration (Figure 2). [32][33][34][35][36][37][38][39][40] However, unfavorable ligand dissociation can become prominent under harsher reaction conditions (e. g., high hydrogen pressure), leading to irreversible ligand decoordination and nanoparticle generation. For example, rhodium nanoparticles have been found to be the active catalyst in an originally thought-to-be homogeneous (CAAC)rhodium-catalyzed arene hydrogenation.…”