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Issue 21, 1999
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Nickel(II)-induced activation of a carbon–nitrogen single bond(s) of a co-ordinated ligand by hydroxylated substrates: generation of mono- and bi-nuclear complexes with modified ligand frameworks

Abstract

In the presence of some hydroxylated compounds as substrates, complexations of nickel(II) with the pentadentate N4S ligand methyl 2-{2-bis[(3,5-dimethylpyrazol-1-ylmethyl)amino]propylamino}cyclopent-1-ene-1-carbodithioate (Hmmpcd) having a pair of flexible pyrazolyl arms proceeded through unusual reaction paths involving C–N bond cleavage process. For example, the product 1 obtained in methanol as substrate is a square planar compound with a modified ligand structure that includes a methoxy group provided by the solvent. With an acidic substrate viz. phenol the product is also a square planar compound 2 with one of the pendant arms of Hmmpcd being replaced by a hydrogen atom. On the other hand, in the presence of a basic substrate viz. ethanolamine the ligand undergoes more extensive breakdown to generate a binuclear complex 3 with a bridging pyrazolyl group. These complexes 1–3 were characterised by X-ray crystallography and 1H NMR spectroscopy. Compound 1 displayed a reversible one-electron NiII → NiI reduction at E½ ≈ –1.0 V vs. Ag–AgCl reference as established by cyclic voltammetry and combined coulometry/EPR experiments. Such reversibility of electron transfer is unusual for a square-planar nickel(II) compound in an acyclic ligand environment. Stabilisation of the reduced nickel(I) species by methoxy group co-ordination provides a probable explanation for this reversible electron transfer.

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Article information


J. Chem. Soc., Dalton Trans., 1999, 3859-3865
Article type
Paper

Nickel(II)-induced activation of a carbon–nitrogen single bond(s) of a co-ordinated ligand by hydroxylated substrates: generation of mono- and bi-nuclear complexes with modified ligand frameworks

S. Bhattacharyya, D. Ghosh, A. Endo, K. Shimizu, T. J. R. Weakley and M. Chaudhury, J. Chem. Soc., Dalton Trans., 1999, 3859 DOI: 10.1039/A905268B

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