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)(mu-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)](2)I(thf)(2). Switching to Yb[N(SiMe3)(2)](2)(thf)(2), the aforementioned oxidants generated monomeric five-coordinate complexes Yb[N(SiMe3)(2)](2)X(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)}(3)Cl][(thf)(5)Eu(mu-Cl)(2)Eu(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)(mu-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)(mu-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)]I-2(thf)(3).