How Changing the Bridgehead Can Affect the Properties of Tripodal Ligands.
Angewandte Chemie (International ed. in English)
John Wiley & Sons Ltd.
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Plajer, A., Colebatch, A., Rizzuto, F., Pröhm, P., Bond, A., García-Rodríguez, R., & Wright, D. (2018). How Changing the Bridgehead Can Affect the Properties of Tripodal Ligands.. Angewandte Chemie (International ed. in English), 57 (22), 6648-6652. https://doi.org/10.1002/anie.201802350
Although a multitude of studies have explored the coordination chemistry of classical tripodal ligands containing a range of main group bridgehead atoms or groups, there has been no clear answer to the question of how underlying periodic trends affect ligand character and reactivity within a single ligand family. In addition to standard steric and electronic modification of the organic groups themselves, this issue is of key importance in the design and tuning of C3-symmetric tripodal ligands for applications in catalysis. A case in point is the extensive family of neutral tris-2-pyridyl ligands E(2-py)3 (e.g., E = C-R, N, P), which are closely related to archetypal tris-pyrazolyl borates. With the new 6-methyl substituted ligands E(6-Me-2-py)3 (E = As, Sb, Bi) in hand, we have been able to assess the effects of bridgehead modification alone on descending a single group in the periodic table. We show that the primary influence on coordination behaviour is the increasing Lewis acidity (electropositivity) of the bridgehead atom as Group 15 is descended, which not only modulates the electron density on the pyridyl donor groups but also introduces the potential for anion selective coordination behavior.
We thank The Leverhulme Trust (Grant for DSW and RG-R, postdoctoral fundng for ALC), The Spanish MINECO-AEI and The EU (ESF) for a Ramon y Cajal contract (RG-R, RYC-2015-19035) and The Cambridge Trust (Vice Chancellor Scholarship for AJP, Cambridge Australia Scholarship for FJR) for financial support. We also thank the ZEDAT and FU Berlin (PP).
External DOI: https://doi.org/10.1002/anie.201802350
This record's URL: https://www.repository.cam.ac.uk/handle/1810/277095