Visualizing the electronic structure of a nickel complex catalyst

Proposing catalytic reaction mechanisms to enable synthesis of new chiral molecules

Like the left hand and the right hand, mirror-image chiral (asymmetrical) molecules cannot be superimposed. In biology, nucleic acids (DNA, RNA) are composed of d-sugars, while proteins are mostly l-amino acids. Since living organisms can recognize the structural difference between left- and right-handed molecules, the preparation of chiral molecules that can selectively interact with biopolymers is vital to pharmaceutical and pesticide manufacturing. However, to date there have been few experimental studies on the electronic structures of metal complex catalysts aimed at investigating the mechanism how these catalysts activate reaction substrates.

 In joint research led by RIKEN CSRS and the RIKEN Center for Emergent Material Science (CEMS), researchers cooperatively developed a nickel complex catalyst to realize an asymmetric [3+2] cycloaddition reaction and carried out an X-ray crystallographic analysis. This analysis revealed that the developed Ni(II) catalyst exhibits distorted octahedral structure with Λ-chirality at the nickel center. Researchers also successfully visualize an electron-deficient dz2 orbital by means of electron density distribution analysis. Additionally, verification of spectrums obtained with spectrographic techniques, together with computational chemistry, indicated that the nickel complex maintained its distorted octahedral structure in solution. The catalyst facilitated synthesis of new chiral molecules with substitution group patterns that differ from existing molecules. Through a series of analytical methods, the researchers were also able to understand both experimentally and quantitatively how the nickel complex catalyst activates the reaction substrates.

These results are expected to lead to logical and efficient development of future metal complex catalysts.

 

Original article
Nature Communications doi:10.1038/NCOMMS14875
Y. Sohtome, G. Nakamura, A. Muranaka, D. Hashizume, S. Lectard, T. Tsuchimoto, M. Uchiyama, M. Sodeoka,
"Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2] cycloaddition".

Contact
Yoshihiro Sohtome; Research Scientist
Mikiko Sodeoka; Group Director
Catalysis and Integrated Research Group