Australian Journal of Chemistry Australian Journal of Chemistry Society
An international journal for chemical science
RESEARCH ARTICLE

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 [CoII2CoIII2(OAc)2(L)2(HL)] (1) and [CoIICoIII4(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 Si = 3/2. Fitting the data to the Heisenberg exchange Hamiltonian (Ĥex = –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.


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