New homoleptic rare‐earth metal complexes comprising the unsymmetrically substituted amidinate ligand [MeC(NEt)(NtBu)] -

Abstract

New homoleptic complexes of selected rare-earth elements containing the unsymmetrically substituted amidinate ligand [MeC(NEt)(NtBu)]– [= (L)–] were synthesized and fully characterized. Treatment of in situ-prepared Li(L) (1) with anhydrous lanthanide(III) chlorides, LnCl3 (Ln = Sc, La, Ce, Ho), afforded three different types of amidinate complexes depending on the ionic radius of the central metal atom. The large La3+ formed the octa-coordinate DME solvate La(L)3(DME) (2). Using Ce3+, the octa-coordinate “ate” complex Li(THF)[Ce(L)4] (3) was formed. Depending on the crystallization conditions, compound 3 could be crystallized in two modifications differing in the coordination environment around Li. In the case of the smaller Sc3+ and Ho3+ ions, six-coordinate homoleptic Sc(L)3 (4) and Ho(L)3 (5) were isolated. The title compounds were fully characterized by spectroscopic and analytical methods as well as single-crystal X-ray diffraction. With Ln = La and Ce, several by-products incorporating lithium, chlorine and/or oxygen were also isolated and structurally characterized.