Cobalt Complexes of Tripodal Hexadentate Ligands: Electrochemically Driven Rearrangements

Paul V. Bernhardt; Yang Kim; Sujandi

doi:10.1071/CH06257

RESEARCH ARTICLE

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Cobalt Complexes of Tripodal Hexadentate Ligands: Electrochemically Driven Rearrangements

Paul V. Bernhardt ^A ^C , Yang Kim ^B and Sujandi ^B

+ Author Affiliations

- Author Affiliations

^A Department of Chemistry, University of Queensland, Brisbane QLD 4072, Australia.

^B Department of Chemistry and Advanced Materials, Kosin University, Busan 606-701, Korea.

^C Corresponding author. Email: p.bernhardt@uq.edu.au

Australian Journal of Chemistry 59(11) 783-790 https://doi.org/10.1071/CH06257
Submitted: 20 July 2006 Accepted: 3 October 2006 Published: 17 November 2006

Abstract

The Co^III complexes of the hexadentate tripodal ligands HOsen (3-(2´-aminoethylamino)-2,2-bis((2´´-aminoethylamino)methyl)propan-1-ol) and HOten (3-(2´-aminoethylthia)-2,2-bis((2´´-aminoethylthia)methyl)propan-1-ol) have been synthesized and fully characterized. The crystal structures of [Co(HOsen)]Cl₃∙H₂O and [Co(HOten)](ClO₄)Cl₂ are reported and in both cases the ligands coordinate as tripodal hexadentate N₆ and N₃S₃ donors, respectively. Cyclic voltammetry of the N₃S₃ coordinated complex [Co(HOten)]³⁺ is complicated and electrode dependent. On a Pt working electrode an irreversible Co^III/II couple (formal potential –157 mV versus Ag|AgCl) is seen, which is indicative of dissociation of the divalent complex formed at the electrode. The free HOten released by the dissociation of [Co(HOten)]²⁺ can be recaptured by Hg as shown by cyclic voltammetry experiments on a static Hg drop electrode (or in the presence of Hg²⁺ ions), which leads to the formation of an electroactive Hg^II complex of the N₃S₃ ligand (formal potential +60 mV versus Ag|AgCl). This behaviour is in contrast to the facile and totally reversible voltammetry of the hexaamine complex [Co(HOsen)]³⁺ (formal potential (Co^III/II) –519 mV versus Ag|AgCl), which is uncomplicated by any coupled chemical reactions. A kinetic and thermodynamic analysis of the [Co(HOten)]²⁺/[Hg(HOten)]²⁺ system is presented on the basis of digital simulation of the experimental voltammetric data.

Acknowledgment

We gratefully acknowledge financial support from an Australian Research Council Linkage International Grant (LX0560194).

References

^A Converted from the reported potential versus a saturated calomel electrode by addition of 44 mV.

Cobalt Complexes of Tripodal Hexadentate Ligands: Electrochemically Driven Rearrangements

Abstract

Acknowledgment

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