Heterometallic 3d−4f Alkoxide Precursors for the Synthesis of Binary Oxide Nanomaterials

Abstract

In this study, a new method for the synthesis of heterometallic 3d−4f alkoxides by the direct reaction of metallic lanthanides (La, Pr, Nd, Gd) with MCl2 (M = Mn, Ni, Co) in 2-methoxyethanol was developed. The method was applied to the synthesis of the heterometallic oxo-alkoxide clusters [Ln4Mn2(μ6O)(μ3-OR)8(HOR)xCl6] (Ln = La (1), Nd (2), Gd (3); x = 0, 2, 4); [Pr4M2(μ6-O)(μ3-OR)8(HOR)xCl6] (M = Co (4), Ni (5); x = 2, 4); and [Ln4Mn2(μ3-OH)2(μ3-OR)4(μ-OR)4(μ-Cl)2(HOR)4Cl6] (Ln = La (11) and Pr (12)). Mechanistic investigation led to the isolation of the homo- and heterometallic intermediates [Pr(μ-OR)(μ-Cl)(HOR)Cl]n (6), [Co4(μ3-OR)4(HOR)4Cl4] (7), [Ni4(μ3-OR)4(HOEt)4Cl4] (8), [Mn4(μ3-OR)4(HOR)2(HOEt)2Cl4] (9), and [Nd(HOR)4Cl][CoCl4] (10). In the presence of an external M(II) source at 1100 °C, 1−4 and 12 were selectively converted into binary metal oxide nanomaterials with trigonal or orthorhombic perovskite structures, i.e., LaMnO3, GdMnO3, NdMnO3, Pr0.9MnO3, and PrCoO3. Compound 5 decomposed into a mixture of homo- and heterometallic oxides. The method presented provides a valuable platform for the preparation of advanced heterometallic oxide materials with promising magnetic, luminescence, and/or catalytic applications.