Controlled hydrolysis of lanthanide complexes of the N-donor tripod tris(2-pyridylmethyl)amine versus bisligand complex formation

Louise Natrajan, Jacques Pécaut, Marinella Mazzanti, Colette LeBrun

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    Abstract

    The reaction of the lanthanide salts LnI3(thf)4 and Ln(OTf)3 with tris(2-pyridylmethyl)amine (tpa) was studied in rigorously anhydrous conditions and in the presence of water. Under rigorously anhydrous conditions the successive formation of mono- and bis(tpa) complexes was observed on addition of 1 and 2 equiv of ligand, respectively. Addition of a third ligand equivalent did not yield additional complexes. The mono(tpa) complex [Ce(tpa)l3] (1) and the bis(tpa) complexes [Ln(tpa) 2]X3 (X = I, Ln = La(III) (2), Ln = Ce(III) (3), Ln = Nd(III) (4), Ln = Lu(III) (5); X = OTf, Ln = Eu(III) (6)) were isolated under rigorously anhydrous conditions and their solid-state and solution structures determined. In the presence of water, 1H NMR spectroscopy and ES-MS show that the successive addition of 1-3 equiv of tpa to triflate or iodide salts of the lanthanides results in the formation of mono(tpa) aqua complexes followed by formation of protonated tpa and hydroxo complexes. The solid-state structures of the complexes [Eu(tpa)(H2O)2(OTf) 3] (7), [Eu(tpa)(μ-OH)(OTf)2]2 (8), and [Ce(tpa)(μ-OH)(MeCN)(H2O]2I4 (9) have been determined. The reaction of the bis(tpa) lanthanide complexes with stoichiometric amounts of water yields a facile synthetic route to a family of discrete dimeric hydroxide-bridged lanthanide complexes prepared in a controlled manner. The suggested mechanism for this reaction involves the displacement of one tpa ligand by two water molecules to form the mono(tpa) complex, which subsequently reacts with the noncoordinated tpa to form the dimeric hydroxo species. © 2005 American Chemical Society.
    Original languageEnglish
    Pages (from-to)4756-4765
    Number of pages9
    JournalInorganic Chemistry: including bioinorganic chemistry
    Volume44
    Issue number13
    DOIs
    Publication statusPublished - 27 Jun 2005

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