Mixed-Valent Polynuclear Cobalt Complexes Incorporating Tetradentate Phenoxyamine Ligands

Joo Chuan Ang; Yanyan Mulyana; Chris Ritchie; Rodolphe Clérac; Colette Boskovic

doi:10.1071/CH09256

RESEARCH ARTICLE

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Mixed-Valent Polynuclear Cobalt Complexes Incorporating Tetradentate Phenoxyamine Ligands

Joo Chuan Ang ^A , Yanyan Mulyana ^A , Chris Ritchie ^A , Rodolphe Clérac ^B ^C and Colette Boskovic ^A ^D

+ Author Affiliations

- Author Affiliations

^A School of Chemistry, University of Melbourne, Vic. 3010, Australia.

^B Centre National De La Recherche Scientifique (CNRS), UPR 8641, Centre de Recherche Paul Pascal (CRPP), Equipe ‘Matériaux Moléculaires Magnétiques’, 115 avenue du Dr Albert Schweitzer, Pessac, F-33600, France.

^C Université de Bordeaux, UPR 8641, Pessac, F-33600, France.

^D Corresponding author. Email: c.boskovic@unimelb.edu.au

Australian Journal of Chemistry 62(9) 1124-1129 https://doi.org/10.1071/CH09256
Submitted: 29 April 2009 Accepted: 2 June 2009 Published: 17 September 2009

Abstract

The new potentially tetradentate ligand precursor 2-[(bis(2-hydroxyethyl)amino)methyl]-4,6-bis-tert-butylphenol (H₃L) has been synthesized and characterized. The reaction of H₃L with cobalt(ii) acetate has afforded the novel mixed-valent tetra- and pentanuclear cobalt complexes [Co^II₂Co^III₂(OAc)₂(L)₂(HL)] (1) and [Co^IICo^III₄(OAc)₂(L)₄] (2). Single-crystal X-ray diffraction studies of these complexes indicate different coordination geometries for the divalent cobalt centres in each complex, with distorted trigonal bipyramidal and distorted tetrahedral coordination evident in 1 and 2, respectively. The variable temperature magnetic susceptibility data for complex 1 reveal behaviour dominated by antiferromagnetic coupling between the two cobalt(ii) centres. Their approximate trigonal bipyramidal coordination geometries give rise to a ⁴A′₂ ground term, allowing a spin-only treatment assuming local spin quantum numbers of S_i = 3/2. Fitting the data to the Heisenberg exchange Hamiltonian (Ĥ_ex = –2JS·₁S₂) results in J = –6.9(1) cm^–1 and g = 2.30(5).

Acknowledgements

The present work was supported by the Australian Research Council, the University of Melbourne, the University of Bordeaux, the CNRS, the Region Aquitaine and MAGMANet (NMP3-CT-2005–515767). We thank Robert Gable for helpful discussions.

References

Mixed-Valent Polynuclear Cobalt Complexes Incorporating Tetradentate Phenoxyamine Ligands

Abstract

Acknowledgements

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