“Pincer” Pyridine–Dicarbene–Iridium and -Ruthenium Complexes and Derivatives Thereof

Andreas A. Danopoulos, Pierre Braunstein, Jörg Saßmannshausen, David Pugh, Joseph A. Wright

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Abstract

The cationic pincer-type complexes [IrI(CNMeC)L]X {CNMeC = [2,6-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]-3,5-dimethylpyridine, L = CO, X = PF6 4; L = CH3CN, X = PF6 5; L = pyridine, X = BArF4, ArF = 3,5-bis-trifluoromethyl-phenyl 6}, that were obtained from [IrI(CNMeC)Cl] (1) by displacement of the chloride ligand were structurally characterized. Complexes 4 and 5 adopt square planar, in-plane distorted geometries, and in 6 the metal environment shows substantial pyramidalization. Theoretical calculations of the cations in 4 and 6 reproduce the experimental structures and rationalize their features. 1 undergoes oxidative transformations with CH2Cl2 to cis-[IrIII(CNMeC)(CH2Cl)Cl2] (7) and with PhICl2 to mer-[IrIII(CNMeC)Cl3] (8). The ruthenium derivatives trans-[RuII(CNC)Cl2L] {CNC = [2,6-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]-pyridine, L = pyridine, 10} and [RuII(CNC)(η22-nbd)](X)2. 2L (nbd = 2,5-norbornadiene, L = CH3CN, X = BF4 11), were prepared by the reaction of cis-trans-[RuCl2(nbd)(py)2] and trans-cis-[RuCl2(nbd)(pip)2] (pip = piperidine) with the ligand CNC, respectively; both adopt distorted octahedral structures. The back-bonding in 11 is comparable to that in its precursor complex, indicating minimal contribution of the NHC donors to this effect. Substitution of both chlorides in the known cis-[RuII(CNC)Cl2L] (L = PPh3) by azido ligands gave cis-[RuII(CNC)(N3)2L] (L = PPh3, 12), which by photolytic cleavage of the coordinated N3 failed to produce well-defined complexes.

Original languageEnglish
Pages (from-to)3359-3369
Number of pages11
JournalEuropean Journal of Inorganic Chemistry
Volume2020
Issue number35
Early online date23 Aug 2020
DOIs
Publication statusPublished - 22 Sep 2020

Keywords

  • Carbene ligands
  • Iridium
  • Oxidative addition
  • Pincer complexes
  • Ruthenium
  • Theoretical calculations

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