Oxidation in Nonclassical Organolanthanide Chemistry: Synthesis, Characterization, and X-ray Crystal Structures of Cerium(III) and -(IV) Amides

[Ce(NR2)3] (R = SiMe3) with TeCl4 in tetrahydrofuran solution gave a mixture of two major products in a combined
yield of ca. 50% based on available metal:  (i) the Ce(IV) amide [CeCl(NR2)3] (1), which was isolated as purple
needles and identified on the basis of 1H NMR and mass spectra, microanalysis, and a single-crystal X-ray analysis
[C18H54CeClN3Si6, rhombohedral, R3c (No. 161), a = b = 18.4508(7) Å, c = 16.8934(7) Å, Z = 6]; (ii) unstable
[{Ce(NR2)2(μ-Cl)(thf)}2] (2), as colorless blocks [C32H88Ce2Cl2N4O2Si8, monoclinic, P21/n (No. 14), a = 14.506(3)
Å, b = 13.065(3) Å, c = 16.779(3) Å, β = 113.789(12)°, Z = 2], which readily disproportionated in solution. In
toluene solution, the product 1 was obtained exclusively. The same cerium(III) amide starting material was oxidized
by PBr2Ph3 in diethyl ether solution to give purple [CeBr(NR2)3] (3) [C18H54BrCeN3Si6, rhombohedral, R3c (No.
161), a = b = 18.4113(12) Å, c = 16.9631(17) Å, Z = 6], along with presumed [CeBr3(OEt2)n], which has not
been characterized but with thf, by displacement of the ether ligands, gave [CeBr3(thf)4] (4) [C16H32Br3CeO4, triclinic,
P1̄ (No. 2), a = 8.2536(7) Å, b = 9.4157(5) Å, c = 15.5935(14) Å, α = 79.009(5), β = 87.290(3)°, γ =
74.835(5)°, Z = 2). TeBr4 reacted with [Ce(NR2)3] in thf to give small amounts of 3; the major product (although
only formed in 15% yield) was monomeric [CeBr2(NR2)(thf)3] (5) [C18H42Br2CeNO3Si2, monoclinic, P21/c (No. 14),
a = 14.9421(4) Å, b = 11.8134(5) Å, c = 15.8317(7) Å, α = γ = 120°, β = 92.185(3)°, Z = 4].