Binding polyprotic small molecules with second-sphere hydrogen bonds

Abstract

Second-sphere hydrogen bonds are known for playing significant roles in homogeneous catalysis and in biological processes with metal-containing molecules. In this work, we highlight a tetradentate asymmetric ether-sulfonamidate ligand that facilitates second-sphere hydrogen bonding in transition metal complexes. We explored its ability to bind mono-, di-, tri-, and tetra-protic ligands when supporting a cobalt(II) ion. The structures of three such cobalt complexes containing bound water, ammonia, and hydrazine are presented. Additionally, spectroscopic analysis of a strongly bound hydroxide ion complex is presented. A hydrogen-bonding configuration, not yet observed in crystal structures of this type, resulted in a bridging hydrazine complex with the two cobalt ions separated by a distance of 5 Å.

Graphical Abstract

Keywords:

• Cobalt
• hydrogen-bonding
• second-sphere
• small molecule
• protic ligand

Acknowledgements

The authors would like to acknowledge Appalachian State University Office of Student Research and the Department of Chemistry and Fermentation Sciences for providing funding and facilities to support this research.

Disclosure statement

The authors report there are no competing interests to declare.