Modular Synthesis of Monoanionic PN Ligands Leads to Unexpected Structural Diversity in Lanthanum Chemistry
Benjamin Wittwer1, Florian Hett1, Michael Seidl1
1Faculty of Chemistry and Pharmacy, Institute of General, Inorganic and Theoretical Chemistry, Leopold-Franzens-University Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria.
Abstract:
We report a new synthetic entry to a series of N-substituted anilidophosphine ligands (short HPNR, R = pTol (HPN), 3,5-dimethylphenyl (HPN), 3,5-bis(trifluoromethyl)phenyl (HPN), 2-methoxyphenyl (HPN), diisopropylphenyl (HPN), and adamantyl (HPN)), allowing a detailed tuning of their steric (and electronic) properties. HPN could be converted into their lithium salts LiPN, which are effective precursors for salt metathesis reactions. The new ligands are used for the synthesis of an array of lanthanide complexes using LaCl3(THF)1.2 as a precursor. Depending on the steric bulk of the anilidophosphine ligand, either chloride-bridged dimers of the general formula [(PNR)2La(μ-Cl2)La(PNR)2] (R = pTol (3f), 3,5-dimethylphenyl (3d) and adamantyl (3a)) or mononuclear complexes of the general formula (PNR)2LaCl (R = diisopropylphenyl (3e)) are observed, if the complexation reaction is carried out in toluene. Contrary, if salt metathesis reactions are carried out in dimethoxyethane (DME) as a coordinating solvent, -ate complexes of the general formula [(PNR)2La(μ-Cl2)Li(DME)] (R = Adamantyl (4a) and R = 2-methoxyphenyl (4d)) or [Li(DME)3][(PNR)2LaCl2] (R = 3,5-bis(trifluoromethyl)phenyl (4b), R = pTol (4f) and R = 3,5-dimethylphenyl (4d)) are observed. All ligands and complexes have been thoroughly characterized by 1D and 2D NMR spectroscopy, IR, and X-ray crystallography. Finally, the steric demand of the new anilidophosphine ligands is evaluated using SambVca simulations.
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