Synthesis and Electrochemical Studies of Nickel β-Diketonate Complexes Incorporating Asymmetric Diimine Ligands

Phimphaka Harding; David J. Harding; Nitisastr Soponrat; Kittiya Tinpun; Sirirat Samuadnuan; Harry Adams

doi:10.1071/CH09232

RESEARCH ARTICLE

Synthesis and Electrochemical Studies of Nickel β-Diketonate Complexes Incorporating Asymmetric Diimine Ligands

Phimphaka Harding ^A ^D , David J. Harding ^A ^D , Nitisastr Soponrat ^B , Kittiya Tinpun ^B , Sirirat Samuadnuan ^B and Harry Adams ^C

+ Author Affiliations

- Author Affiliations

^A Molecular Technology Research Unit, School of Science, Walailak University, Thasala, Nakhon Si Thammarat, 80161, Thailand.

^B Department of Chemistry, Faculty of Science, Taksin University, Songkhla, 90000, Thailand.

^C Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, UK.

^D Corresponding authors. Email: kphimpha@wu.ac.th; hdavid@wu.ac.th

Australian Journal of Chemistry 63(1) 75-82 https://doi.org/10.1071/CH09232
Submitted: 20 April 2009 Accepted: 15 July 2009 Published: 8 January 2010

Abstract

The reaction of ppa^X {(4-X-phenyl)-pyridin-2-ylmethylene-amine; X = H, Me, Et, OMe, F, Cl, Br, and I} with [Ni(β-diketonate)₂(H₂O)₂] {β-diketonate = 1,3-diphenylpropanedionate (dbm), 2,2,6,6-tetramethyl-3,5-heptadionate (tmhd), or hexafluoroacetylacetonate (hfac)} yields a series of nickel complexes. X-ray crystallography reveals octahedral coordinated nickel centres with a cis arrangement of the β-diketonate ligands. The β-diketonate ligands adopt ‘planar’ or ‘bent’ coordination modes, whereas the aryl ring of the ppa^X ligand is twisted with respect to the pyridylimine unit. The electrochemical behaviour of the complexes reveals quasi-reversible or irreversible one-electron oxidation to Ni(iii) in the case of the [Ni(tmhd)₂(ppa^X)] and [Ni(dbm)₂(ppa^X)] complexes, respectively. The peak potential for oxidation is dependent on the type of β-diketonate ligand but essentially independent of the substituent, X, on the ppa^X ligand. The [Ni(β-diketonate)₂(ppa^X)] complexes (X = F, Cl, Br, and I) also undergo ligand based reduction.

Acknowledgements

We gratefully acknowledge the Thailand Research Fund and Walailak University (Grant No. RSA5080007) for funding this research. We also thank the School of Chemistry, University of Bristol for elemental analysis and MS services.

References

Synthesis and Electrochemical Studies of Nickel β-Diketonate Complexes Incorporating Asymmetric Diimine Ligands

Abstract

Acknowledgements

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