Oxidation in nonclassical organolanthanide chemistry: synthesis, characterization, and X-ray crystal structures of cerium(III) and -(IV) amides.

[Ce(NR(2))(3)] (R = SiMe(3)) with TeCl(4) 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(NR(2))(3)] (1), which was isolated as purple needles and identified on the basis of (1)H NMR and mass spectra, microanalysis, and a single-crystal X-ray analysis [C(18)H(54)CeClN(3)Si(6), rhombohedral, R3c (No. 161), a = b = 18.4508(7) A, c = 16.8934(7) A, Z = 6]; (ii) unstable [[Ce(NR(2))(2)(mu-Cl)(thf)](2)] (2), as colorless blocks [C(32)H(88)Ce(2)Cl(2)N(4)O(2)Si(8), monoclinic, P2(1)/n (No. 14), a = 14.506(3) A, b = 13.065(3) A, c = 16.779(3) A, beta = 113.789(12) degrees, 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 PBr(2)Ph(3) in diethyl ether solution to give purple [CeBr(NR(2))(3)] (3) [C(18)H(54)BrCeN(3)Si(6), rhombohedral, R3c (No. 161), a = b = 18.4113(12) A, c = 16.9631(17) A, Z = 6], along with presumed [CeBr(3)(OEt(2))(n)()], which has not been characterized but with thf, by displacement of the ether ligands, gave [CeBr(3)(thf)(4)] (4) [C(16)H(32)Br(3)CeO(4), triclinic, P1 (No. 2), a = 8.2536(7) A, b = 9.4157(5) A, c = 15.5935(14) A, alpha = 79.009(5), beta = 87.290(3) degrees, gamma = 74.835(5) degrees, Z = 2). TeBr(4) reacted with [Ce(NR(2))(3)] in thf to give small amounts of 3; the major product (although only formed in 15% yield) was monomeric [CeBr(2)(NR(2))(thf)(3)] (5) [C(18)H(42)Br(2)CeNO(3)Si(2), monoclinic, P2(1)/c (No. 14), a = 14.9421(4) A, b = 11.8134(5) A, c = 15.8317(7) A, alpha = gamma = 120 degrees, beta = 92.185(3) degrees, Z = 4].