Trivalent Rare-Earth-Metal Bis(trimethylsilyl)amide Halide Complexes by Targeted Oxidations

In contrast to previously applied salt metathesis protocols the targeted rare-earth-metal compounds Ln­[N­(SiMe3)2]2(halogenido) were accessed by oxidation of Ln­(II) silylamide precursors. Treatment of Sm­[N­(SiMe3)3]2(thf)2 with 0.5 equiv of C2Cl6 or 0.25 equiv of TeBr4 in thf and crystallization thereof gave [Sm­{N­(SiMe3)2}2(μ-X)­(thf)]2 (X = Cl, Br). A similar reaction/crystallization procedure performed with 0.5 equiv of 1,2-diiodoethane gave monomeric Sm­[N­(SiMe3)2]2I­(thf)2. Switching to Yb­[N­(SiMe3)2]2(thf)2, the aforementioned oxidants generated monomeric five-coordinate complexes Yb­[N­(SiMe3)2]2X­(thf)2 (X = Cl, Br, I). The reaction of Eu­[N­(SiMe3)2]2(thf)2 with 0.5 equiv of C2Cl6 in thf yielded the separated ion pair [Eu­{N­(SiMe3)2}3Cl]­[(thf)5Eu­(μ-Cl)2Eu­(thf)5]. Performing the chlorination in n-hexane led to oxidation followed by rapid disproportionation into EuCl3(thf) x and Eu­[N­(SiMe3)2]3. The bromination reaction did not afford crystalline material, while the iodination gave crystals of divalent EuI2(thf)5. Use of trityl chloride (Ph3CCl) as the oxidant in thf accomplished the Eu­(III) species [Eu­{N­(SiMe3)2}2(μ-Cl)­(thf)]2. In situ oxidation of putative [Tm­{N­(SiMe3)2}2(thf) x ] using 0.5 equiv of C2Cl6 in thf followed by crystallization from n-hexane led to the formation of a mixture of [Tm­{N­(SiMe3)2}2(μ-Cl)­(thf)]2 and Tm­[N­(SiMe3)2]3. Switching the oxidant to 0.5 equiv of 1,2-diiodoethane and crystallizing from thf repeatedly afforded the bis-halogenated complex Tm­[N­(SiMe3)2]­I2(thf)3.