A Bidentate Ligand Featuring Ditopic Lewis Acids in the Second Sphere for Selective Substrate Capture and Activation

Daniel M Beagan; John J Kiernicki; Matthias Zeller; Nathaniel K Szymczak

doi:10.1002/anie.202218907

A Bidentate Ligand Featuring Ditopic Lewis Acids in the Second Sphere for Selective Substrate Capture and Activation

Angew Chem Int Ed Engl. 2023 Mar 20;62(13):e202218907. doi: 10.1002/anie.202218907. Epub 2023 Feb 20.

Authors

Daniel M Beagan¹, John J Kiernicki^{1

2}, Matthias Zeller³, Nathaniel K Szymczak¹

Affiliations

¹ Department of Chemistry, University of Michigan, 930 N. University, Ann Arbor, MI 48109, USA.
² Present address: Drury University, Department of Chemistry and Physics, 900 North Benton Ave., Springfield, MO 65802, USA.
³ H.C. Brown Laboratory, Department of Chemistry, Purdue University, 560 Oval Dr., West Lafayette, IN 47907, USA.

Abstract

We present a ligand platform featuring appended ditopic Lewis acids to facilitate capture/activation of diatomic substrates. We show that incorporation of two 9-borabicyclo[3.3.1]nonane (9-BBN) units on a single carbon tethered to a pyridine pyrazole scaffold maintains a set of unquenched nitrogen donors available to coordinate Fe^II , Zn^II , and Ni^II . Using hydride ion affinity and competition experiments, we establish an additive effect for ditopic secondary sphere boranes, compared to the monotopic analogue. These effects are exploited to achieve high selectivity for binding NO₂ ^- in the presence of competitive anions such as F^- and NO₃ ^- . Finally, we demonstrate hydrazine capture within the second-sphere of metal complexes, followed by unique activation pathways to generate hydrazido and diazene ligands on Zn and Fe, respectively.

Keywords: Chemoselective Anion Binding; Ditopic Boranes; Hydrazine Functionalization; Lewis Acids; Secondary Coordination Sphere.

Abstract

Grants and funding