Supramolecular Anchoring of NCN-Pincer Palladium Complexes into a β-Barrel Protein Host: Molecular-Docking and Reactivity Insights

Lucrèce Pocquet, Nikolay Vologdin, Giuseppe Felice Mangiatordi, Ilaria Ciofini, Orazio Nicolotti, Serge Thorimbert, Michèle Salmain
  • European Journal of Inorganic Chemistry, July 2017, Wiley
  • DOI: 10.1002/ejic.201700365

What is it about?

Several prochiral NCN-pincer complexes of palladium(II), with hemilabile ligands and a long aliphatic chain, were synthesized and characterized spectroscopically. In some of the complexes, the presence of two different substituents on the N donor atoms made them stereogenic, so that they were isolated as a mixture of diastereoisomers, which could be differentiated by 1H NMR spectroscopy. Binding of some of these complexes to bovine -lactoglobin by insertion within its inner cavity was theoretically investigated by molecular-docking simulation and was experimentally confirmed by CD spectroscopy. Adjunction of H-bond donor substituents on the ligand framework gave more-stable supramolecular protein–complex assemblies. These constructs were shown to catalyze aldol condensation reactions in aqueous media, affording, in some cases, the less-favorable cis product. Since the corresponding complexes exclusively gave the trans product in the absence of -lactoglobulin, this unusual diastereoselectivity was ensued by the second sphere of coordination brought by the protein host.

Why is it important?

This paper has been highlighted as VIP by the editor. We demonstrate that hemilabile ligands around a metal could adapt to the protein host and then influence the stereochemical outcome of a metal-catalyzed reaction.


Professor Serge THORIMBERT
Sorbonne Université

We are currently adapting this approach to other metal-catalyzed reactions in which enantioselectivity is controlled in an efficient manner.

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