Facile Synthesis and Versatile Reactivity of an Unusual Cyclometalated Rhodium(I) Pincer Complex |
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| Authors: | Linda S Jongbloed Prof?Dr Bas de?Bruin Prof?Dr Joost N H Reek Dr Martin Lutz Dr?Ir Jarl Ivar van der Vlugt |
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| Affiliation: | 1. Homogeneous, Bioinspired and Supramolecular Catalysis van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (The Netherlands);2. Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht (The Netherlands) |
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| Abstract: | The synthesis of the reactive PN(CH) ligand 2‐di(tert‐butylphosphanomethyl)‐6‐phenylpyridine ( 1H ) and its versatile coordination to a RhI center is described. Facile C?H activation occurs in the presence of a (internal) base, thus resulting in the new cyclometalated complex RhI(CO)(κ3‐P,N,C‐ 1 )] ( 3 ), which has been structurally characterized. The resulting tridentate ligand framework was experimentally and computationally shown to display dual‐site proton‐responsive reactivity, including reversible cyclometalation. This feature was probed by selective H/D exchange with D1]formic acid. The addition of HBF4 to 3 leads to rapid net protonolysis of the Rh?C bond to produce RhI(CO)(κ3‐P,N,(C?H)‐ 1 )] ( 4 ). This species features a rare aryl C?H agostic interaction in the solid state, as shown by X‐ray diffraction studies. The nature of this interaction was also studied computationally. Reaction of 3 with methyl iodide results in rapid and selective ortho‐methylation of the phenyl ring, thus generating RhI(CO)(κ2‐P,N‐ 1Me )] ( 5 ). Variable‐temperature NMR spectroscopy indicates the involvement of a RhIII intermediate through formal oxidative addition to give trans‐RhIII(CH3)(CO)(I)(κ3‐P,N,C‐ 1 )] prior to C?C reductive elimination. The RhIII–trans‐diiodide complex RhI(CO)(I)2(κ3‐P,N,C‐ 1 )] ( 6 ) has been structurally characterized as a model compound for this elusive intermediate. |
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| Keywords: | C H activation metallacycles pincers reactive ligands rhodium |
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