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)(η2,η2‐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.

Highlights

  • Complexes with pincer architectures and Nheterocyclic carbene donors have appeared early in the development of the NHC coordination chemistry,[1] there is currently growing research interest in the area.[2]

  • The NMR spectroscopic data are in line with a square planar monocarbonyl complex with signals at δ 193.08 (Ir-CO) and δ 189.69 (Ir-CNHC)

  • A detailed study was undertaken with the complex [IrI(CNMeC)Py][BAr4F] (6) that was obtained by the substitution of the chloride in 1 with pyridine and anion exchange with [BArF4]-.REF The 1H-NMR spectrum of 6 is in accord with a structure having only one plane of symmetry; this concurred with the presence of one signal assignable to CNHC in the 13C{1H}-NMR spectrum and another for the methyl groups attached to the pyridine bridgehead

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Summary

Introduction

Complexes with pincer architectures and Nheterocyclic carbene donors (almost exclusively imidazol-2ylidenes) have appeared early in the development of the NHC coordination chemistry,[1] there is currently growing research interest in the area.[2]. A detailed study was undertaken with the complex [IrI(CNMeC)Py][BAr4F] (6) that was obtained by the substitution of the chloride in 1 with pyridine and anion exchange with [BArF4]-.REF The 1H-NMR spectrum of 6 is in accord with a structure having only one plane of symmetry (perpendicular to the coordination plane); this concurred with the presence of one signal assignable to CNHC in the 13C{1H}-NMR spectrum and another for the methyl groups attached to the pyridine bridgehead.

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