We are reporting activation of various substrates facilitated by early transition metal halide acting as strong Lewis acids (TaCl5, NbCl5) and organic Lewis bases (NEt3, PPh3, etc). This talk will entail the activation of C-H bonds in both alkyl and aryl nitriles by the TaCl5- PPh3 Lewis pair and their transformation into novel zwitterionic vinyl imido complexes. Increase of steric hindrance of a nitrile substrate resulted in another reaction pathway leading to coupling of nitriles through C-C single bond formation. Aryl-nitriles were reacted with the TaCl5- PPh3 Lewis pair through aromatic C-H bond activation and conversion to imido species. In case of benzonitrile, dimerization of these imido complexes through C=C double bond formation was observed in reaction with stronger bases. C–O bonds of organic ethers were selectively activated by the presented Lewis acid-base systems. Remarkably, all the reported activation processes appear to proceed through cooperative Lewis acid-Lewis base interactions and do not involve redox events at the metal center.

Activation of C-H and C-O bonds by the TaCl5-PPh3 cooperative Lewis pair

256th National Meeting (2018)

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