Reversible 1,2-Alkyl Migration to Carbene and Ammonia Activation in an N-Heterocyclic Carbene-Zirconium Complex

Emmanuelle Despagnet-Ayoub; Michael K Takase; Jay A Labinger; John E Bercaw

doi:10.1021/jacs.5b06695

Reversible 1,2-Alkyl Migration to Carbene and Ammonia Activation in an N-Heterocyclic Carbene-Zirconium Complex

J Am Chem Soc. 2015 Aug 26;137(33):10500-3. doi: 10.1021/jacs.5b06695. Epub 2015 Aug 17.

Authors

Emmanuelle Despagnet-Ayoub¹, Michael K Takase¹, Jay A Labinger¹, John E Bercaw¹

Affiliation

¹ Arnold and Mabel Beckman Laboratories of Chemical Synthesis, California Institute of Technology , Pasadena, California 91125, United States.

PMID: 26251373
DOI: 10.1021/jacs.5b06695

Abstract

Addition of trimethylphosphine to a bis(phenolate)benzylimidazolylidene(dibenzyl)zirconium complex induces migration of a benzyl ligand from the metal center to the C(carbine) atom. This process may be reversed, resulting in Csp(3)-Csp(3) activation, by abstraction of the phosphine, an example of regulated, reversible alkyl migration. Addition of ammonia to the dibenzyl complex results in migration of one benzyl group and protonolysis of the other to generate a bis(NH2)-bridged dimer via an NMR-observable intermediate NH3 adduct.