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Issue 44, 2016
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Spin-state diversity in a series of Co(II) PNP pincer bromide complexes

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We describe the structural and electronic impacts of modifying the bridging atom in a family of Co(II) pincer complexes with the formula Co(t-Bu)2PEPyEP(t-Bu)2Br2 (Py = pyridine, E = CH2, NH, and O for compounds 1–3, respectively). Structural characterization by single crystal X-ray diffraction indicates that compounds 1 and 3 are 5-coordinate complexes with both bromides bound to the Co(II) ion, while compound 2 is square planar with one bromide in the outer coordination sphere. The reduction potentials of 1–3, characterized by cyclic voltammetry, are consistent with the increasing electron-withdrawing character of the pincer ligand as the linker (E) between the pyridine and phosphine arms becomes more electronegative. Magnetic property studies of compounds 1 and 2 confirm high- and low-spin behavior, respectively, through a broad temperature range. However, complex 3 features an unusual combination of high spin S = 3/2 Co(II) and temperature dependent spin-crossover between S = 3/2 and S = 1/2 states. The different magnetic behaviors observed among the three CoBr2 pincer complexes reflects the importance of small ligand perturbations on overall coordination geometry and resulting spin state properties.

Graphical abstract: Spin-state diversity in a series of Co(ii) PNP pincer bromide complexes

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The article was received on 05 Sep 2016, accepted on 13 Oct 2016 and first published on 13 Oct 2016

Article type: Paper
DOI: 10.1039/C6DT03461F
Citation: Dalton Trans., 2016,45, 17910-17917
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    Spin-state diversity in a series of Co(II) PNP pincer bromide complexes

    D. W. Shaffer, I. Bhowmick, A. L. Rheingold, C. Tsay, B. N. Livesay, M. P. Shores and J. Y. Yang, Dalton Trans., 2016, 45, 17910
    DOI: 10.1039/C6DT03461F

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