An iron(ii) spin-crossover metallacycle from a back-to-back bis-[dipyrazolylpyridine]

Laurence J. Kershaw Cook, Julie Fisher, Lindsay P. Harding, Malcolm A. Halcrow

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


The syntheses of 4-mercapto-2,6-di(pyrazol-1-yl)pyridine (bppSH) and bis[2,6-di(pyrazol-1-yl)pyrid-4-yl]disulfide (bppSSbpp) are reported. In contrast to previously published "back-to-back" bis-[2,6-di(pyrazol-1-yl)pyridine] derivatives, which form coordination polymers with transition ions that are usually insoluble, bppSSbpp yields soluble oligomeric complexes with iron(ii) and zinc(ii). Mass spectrometry and DOSY data show that [{Fe(μ-bppSSbpp)}n]2n+ and [{Zn(μ-bppSSbpp)}n]2n+ form tetranuclear metallacycles in nitromethane solution (n = 4), although 1H NMR and conductivity measurements imply the iron compound may undergo more fragmentation than its zinc congener. Both [{Fe(bppSH)2]2+ and [{Fe(μ-bppSSbpp)}n]2n+ exhibit thermal spin-crossover in CD3NO2 solution, with midpoint temperatures near 245 K. The similarity of these equilibria implies there is little cooperativity between the iron centres in the metallacyclic structures.

Original languageEnglish
Pages (from-to)9417-9425
Number of pages9
JournalDalton Transactions
Issue number20
Early online date16 Apr 2015
Publication statusPublished - 28 May 2015


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