Synthesis and Coordination Chemistry of Doubly-Tridentate Tripodal Pyridazine and Pyrimidine-Derived Ligands: Structural Interplay Between M2L and M2L2 (M = Ni and Pd) Complexes and Magnetic Properties of Iron(ii) Complexes

Christopher J. Sumby; Ben A. Leita; Boujemaa Moubaraki; Keith S. Murray; Peter J. Steel

doi:10.1071/CH09244

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Synthesis and Coordination Chemistry of Doubly-Tridentate Tripodal Pyridazine and Pyrimidine-Derived Ligands: Structural Interplay Between M₂L and M₂L₂ (M = Ni and Pd) Complexes and Magnetic Properties of Iron(ii) Complexes

Christopher J. Sumby ^A ^B ^D , Ben A. Leita ^C , Boujemaa Moubaraki ^C , Keith S. Murray ^C and Peter J. Steel ^A

+ Author Affiliations

- Author Affiliations

^A Department of Chemistry, College of Science, University of Canterbury, Christchurch, New Zealand.

^B Current address: School of Chemistry and Physics, University of Adelaide, Adelaide, SA 5005, Australia.

^C School of Chemistry, Monash University, Clayton, Vic. 3800, Australia.

^D Corresponding author. Email: christopher.sumby@adelaide.edu.au

Australian Journal of Chemistry 62(9) 1142-1154 https://doi.org/10.1071/CH09244
Submitted: 25 April 2009 Accepted: 16 July 2009 Published: 17 September 2009

Abstract

The coordination chemistry of three bridging doubly-tridentate ligands, including the known compound 3,6-bis(di-2-pyridylmethyl)pyridazine (1), which is structurally similar to 1,4-bis(di-2-pyridylmethyl)phthalazine (2), and two pyrimidine-linked compounds 4,6-bis(di-2-pyridylmethyl)pyrimidine (3), and 4,6-bis(di-2-pyridylamino)pyrimidine (4), was investigated with Fe^II, Ni^II, and Pd^II metal salts. Ligands 3 and 4 were synthesized in one-pot reactions from easily obtained starting materials; compound 3 was synthesized from di-2-pyridylmethane and 4,6-diiodopyrimidine in 48% yield, while ligand 4 was prepared by reacting di-2-pyridylamine with 4,6-dichloropyrimidine in 27% yield. During the synthesis of 4, an additional compound, 4-chloro-6-(di-2-pyridylamino)pyrimidine (5), with only one tridentate binding site was obtained in 30% yield. Reactions of 1, 3, and 4 with Fe^II or Ni^II salts gave two types of complexes, either discrete M₂L or M₂L₂ assemblies. The Pd^II complexes obtained were also characterized as discrete M₂L complexes. The compounds were characterized by a combination of NMR and IR spectroscopy, microanalysis and X-ray crystallography. Noticeable differences in the structures obtained for Ni^II coordination complexes with the carbon-linked (3) and nitrogen-linked (4) ligands were observed, whereby the nitrogen linker adopted a trigonal planar geometry and prevented tridentate facial coordination of the octahedral metal centres. The magnetic properties of dinuclear Fe^II complexes of 1 were examined to see if they showed spin-crossover effects, a feature recently observed by others in other dinuclear helicate complexes, but the complexes remained high-spin at all temperatures between 300 and 2 K.

Acknowledgements

P.J.S. thanks the Royal Society of New Zealand for funding through the Marsden Fund, and a James Cook Research Fellowship. K.S.M. thanks the Australian Research Council for supporting this research.

References

Synthesis and Coordination Chemistry of Doubly-Tridentate Tripodal Pyridazine and Pyrimidine-Derived Ligands: Structural Interplay Between M2L and M2L2 (M = Ni and Pd) Complexes and Magnetic Properties of Iron(ii) Complexes

Abstract

Acknowledgements

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Synthesis and Coordination Chemistry of Doubly-Tridentate Tripodal Pyridazine and Pyrimidine-Derived Ligands: Structural Interplay Between M₂L and M₂L₂ (M = Ni and Pd) Complexes and Magnetic Properties of Iron(ii) Complexes