Synthesis and structural study of a lithium complex of 6-methyl-2-(trimethylsilylamino)pyridine and its use in the formation of some lanthanoid complexes

• Published in: Journal of organometallic chemistry Vol. 665; no. 1; pp. 33 - 42
• Main Authors: Baldamus, Jens, Cole, Marcus L, Helmstedt, Ulrike, Hey-Hawkins, Eva-Marie, Jones, Cameron, Junk, Peter C, Lange, Franziska, Smithies, Neil A
• Format: Journal Article
• Language: English
• Published: LAUSANNE Elsevier B.V 03.01.2003; Elsevier
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Lanthanoid complexes; Lithium complexes; Physical Sciences; Science & Technology; Synthesis and structural study; Lanthanoid complexes; Lithium complexes; Synthesis and structural study; MOLECULAR-STRUCTURE; ORGANOLANTHANOIDS; TRANSMETALLATION REACTIONS; CHEMISTRY; REACTIVITY; CRYSTAL-STRUCTURES; LIGAND; CYCLOPENTADIENYLLANTHANOIDS; lanthanoid complexes; synthesis and structural study; lithium complexes
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(02)02040-5

Lithiation of 6-methyl-2-(trimethylsilylamino)pyridine (APyTMSH) occurs smoothly in tetrahydrofuran (thf) affording [Li(APyTMS)(thf)] 2 ( 1). Treatment of anhydrous lanthanoid chlorides (LnCl 3, Ln=Gd, Er) with 1.5 equivalents of ( 1) yields the solvent-free homoleptic tris–amido complexes [Ln(APyTMS) 3], (Ln=Gd ( 2); Ln=Er ( 3)). Similar treatment of LnCl 3 (Ln=Gd, Er) with one equivalents of 1 putatively generates the heteroleptic species [Ln(APyTMS) 2Cl], (Ln=Gd ( 4); Ln=Er ( 5)) in situ, however, these compounds undergo redistribution in hexane to yield homoleptic 2 and 3 and the anhydrous lanthanoid halides (Ln=Gd, ( 6), Ln=Er ( 7)) and were therefore not fully characterised. These lanthanoid reagents are extremely moisture sensitive as examplified by the low yield isolation of [APyH 2·H] 2[ErCl 5(thf)] during one prepartion of 3. The structures of compounds 1, 2, 3 and 8 were characterised by X-ray crystallographic methods. The X-ray structure of 1 is a centrosymmetric dimer similar to its diethyl ether analogue. Compounds 2 and 3 are six-coordinate homoleptic mononuclear species and compound 8 comprises the unprecedented [ErCl 5(thf)] − anion within an intricate hydrogen-bonded ionic system. Treatment of anhydrous lanthanoid chlorides (LnCl 3, Ln=Gd, Er) with three equivalents of [Li(APyTMS)(thf)] (APyTMSH=6-methyl-2-(trimethylsilylamino)pyridine) yields the solvent-free homoleptic tris–amido complexes [Ln(APyTMS) 3]. Similar treatment of LnCl 3 (Ln=Gd, Er) with two equivalents of [Li(APyTMS)(thf)] putatively generates the heteroleptic species [Ln(APyTMS) 2Cl], however, these compounds undergo redistribution in hexane rendering the homoleptic tris–amido complex [Ln(APyTMS) 3] and the anhydrous lanthanoid halide.