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Issue 43, 2018
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Variable coordination of carbazolyl-bis(tetrazole) ligands in lanthanide chemistry

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The synthesis of the protioligand 1,8-bis(2′-isopropyltetrazo-5′-yl)-3,6-di-tert-butylcarbazole, HCzTiPr2, is described. The acid–base reaction of 2 with various Ln[N(SiMe3)2]3 (Ln = Ce, Sm, Er, Yb, Y) precursors leads to products displaying a variety of different bonding modes for the CzTiPr− ligand as revealed by X-ray crystallographic studies. The smaller lanthanides form Ln(CzTiPr)[N(SiMe3)2]2 complexes (Ln = Er (3), Yb(4)) with a near planar, tridentate coordination mode for the CzTiPr− ligand. In contrast, the larger lanthanides form Ln(CzTiPr)2[N(SiMe3)2] complexes (Ln = Ce (5), Sm (6)) at room temperature that feature a sandwich structure with a highly distorted tridentate mode where tetrazole canting allows the metal to sit well out of the carbazole plane. Attempts to force additional CzTiPr− ligands onto Er or Yb at elevated temperature results in isolation of trace siloxide complexes Ln(CzTiPr)2(OSiMe3) (Ln = Er (3a), Yb (4a)) that adopt a flat tridentate ligand bonding mode similar to 3 and 4. Surprisingly, the high temperature reaction of 2 with Y[N(SiMe3)2]3 affords Y(CzTiPr)3, 7, featuring two tridentate and one bidentate CzTiPr ligands. Partial hydrolysis of 6 occurs over time to produce a hydroxo-bridged dimer that also features one bridging and one bidentate CzTiPr ligand, Sm(κ3-CzTiPr)(κ3-μ-CzTiPr)(μ-OH)2Sm(κ3-CzTiPr)(κ2-CzTiPr), 6a, further illustrating the remarkable coordinative flexibility of the CzTiPr ligand system.

Graphical abstract: Variable coordination of carbazolyl-bis(tetrazole) ligands in lanthanide chemistry

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Publication details

The article was received on 06 Jul 2018, accepted on 12 Oct 2018 and first published on 12 Oct 2018

Article type: Paper
DOI: 10.1039/C8DT02757A
Citation: Dalton Trans., 2018,47, 15487-15496

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    Variable coordination of carbazolyl-bis(tetrazole) ligands in lanthanide chemistry

    L. Gajecki, D. J. Berg, J. Hoenisch and A. G. Oliver, Dalton Trans., 2018, 47, 15487
    DOI: 10.1039/C8DT02757A

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