Trivalent Rare-Earth-Metal Bis(trimethylsilyl)amide Halide Complexes by Targeted Oxidations
journal contribution
posted on 2018-04-09, 17:24 authored by André M. Bienfait, Benjamin M. Wolf, Karl W. Törnroos, Reiner AnwanderIn 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.
