Preparation and Structure of Mono- and Binuclear Half-Sandwich Iridium, Ruthenium, and Rhodium Carbene Complexes Containing 1,2-Dichalcogenolao 1,2-Dicarba-closo-Dodecaboranes

The synthesis of half‐sandwich transition metal complexes containing both 1,2‐dichalcogenolato‐1,2‐dicarba‐closo‐docecaborane (CabE,E) [CabE,E=E2C2(B10H10); E = S, Se] and N‐heterocyclic carbene (NHC) ligands is described. Addition of mono‐NHC ligand to the 16e half‐sandwich dichalcogenolato carborane complexes [Cp*Rh(CabE,E)], [Cp*Ir(CabS,S)], [(p‐cymene)Ru(CabS,S)] (Cp* = pentamethylcyclopentadienyl) gives corresponding mononuclear 18e dithiolate complexes of the type [LM(CabE,E)(NHC)]: [Cp*M(CabS,S)(1‐ethenyl‐3‐methylimidazolin‐2‐ylidene)] (M = Ir (2), Rh (3)), [Cp*Rh(CabE,E)(3‐methyl‐1‐picolyimidazolin‐2‐ylidene)] [E = S (6), Se (7)], [(p‐cymene)Ru(CabS,S)(NHC)] [NHC = 1‐ethenyl‐3‐methylimidazolin‐2‐ylidene (4), 3‐methyl‐1‐picolyimidazolin‐2‐ylidene (8)], whereas bis‐NHC give centrosymmetric binuclear complexes [{Cp*M(CabS,S)}2(1,1′‐dimethyl‐3,3′‐methylene(imidazolin‐2‐ylidene))] [M = Rh (10), Ir (11)]. The complexes were characterized by IR, NMR spectroscopy and elemental analysis. In addition, X‐ray structure analyses were performed on complexes 2–4, 6, 8, 10 and 11. Half‐sandwich Ir, Rh, and Ru carbene complexes (2, 3, 5, and 6) containing 1,2‐dichalcogenolato carborane ligands have been synthesized (see scheme) and characterized structurally. Addition of mono‐N‐heterocyclic carbenes such as 1 yielded mononuclear compounds 2 and 3, where bis‐NHC ligands yielded centrosymmetric binuclear complexes (5 and 6).