Pincer Pyridine-Dicarbene-Iridium and -Ruthenium Complexes and Derivatives Thereof

The cationic pincer-type complexes [Ir-I((CNC)-C-Me)L]X {(CNC)-C-Me = [2,6-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]-3,5-dimethylpyridine, L = CO, X = PF(6)4; L = CH3CN, X = PF(6)5; L = pyridine, X = BAr4F, Ar-F= 3,5-bis-trifluoromethyl-phenyl6}, that were obtained from [Ir-I((CNC)-C-Me)Cl] (1) by displacement of the chloride ligand were structurally characterized. Complexes4and5adopt square planar, in-plane distorted geometries, and in6the metal environment shows substantial pyramidalization. Theoretical calculations of the cations in4and6reproduce the experimental structures and rationalize their features.1undergoes oxidative transformations with CH(2)Cl(2)tocis-[Ir-III((CNC)-C-Me)(CH2Cl)Cl-2] (7) and with PhICl(2)tomer-[Ir-III((CNC)-C-Me)Cl-3] (8). The ruthenium derivativestrans-[Ru-II(CNC)Cl2L] {CNC = [2,6-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]-pyridine, L = pyridine,10} and [Ru-II(CNC)(eta(2),eta(2)-nbd)](X)(2). 2L (nbd = 2,5-norbornadiene, L = CH3CN, X = BF(4)11), were prepared by the reaction ofcis-trans-[RuCl2(nbd)(py)(2)] andtrans-cis-[RuCl2(nbd)(pip)(2)] (pip = piperidine) with the ligand CNC, respectively; both adopt distorted octahedral structures. The back-bonding in11is comparable to that in its precursor complex, indicating minimal contribution of the NHC donors to this effect. Substitution of both chlorides in the knowncis-[Ru-II(CNC)Cl2L] (L = PPh3) by azido ligands gavecis-[Ru-II(CNC)(N-3)(2)L] (L = PPh3,12), which by photolytic cleavage of the coordinated N(3)failed to produce well-defined complexes.