Complexes [Ce(NR2)3] (1) or [Ce(NR″2)3] (2) were cerium(III) precursors to the X-ray characterised crystalline oligomeric oxygen-containing amidocerium(IV) compounds [{Ce(NR2)2(μ-O)}n] (3, n = 2; 4, n = 3), [{Ce(NR″2)2(μ-O)}4] (5), [{(R2N)3Ce}2(μ-
OMOM
)] (6, M = Na; 7, M = K), [{(R2N)3CeOCe(NR2)2}2(μ-
OKOK
)] (8), and [{Ce(NR2)3}2(μ-η2:η2-O2)]·2CnH2n+2 (9, n = 6; 9′, n = 5) [R = SiMe3, NR″2 = TMP =
NC(Me)2(CH2)3C
Me2]. Each was isolated in low, or for 5 very low, yield. Except for 4, the oxidising agent was O2 at −27 °C in hexane (3, 6, 7, 8, 9), pentane (9′), or toluene (5), and a co-reagent for the alkali metal bis(trimethylsilyl)amido(oxy)cerate(IV)s was NaNR2 (8) or KNR2 (7, 8). From 1 and an equivalent portion of 2,6-tBu2-benzoquinone after 5 weeks in pentane there was obtained the bis(amido)cyclotricer(IV)oxane 4. The NMR spectral solution chemical shifts for NR2 groups of 3, 4, and 6–9 were consistent with each sample being diamagnetic and hence a Ce(IV) species. A transient amidocerium(IV) superoxide Ce(NR2)3(η2-O2) (J), or its TMP analogue, is considered to be the common first-formed intermediate in each case, while 4 is believed to have arisen from the adventitious hydrolysis of [{Ce(NR2)3O}2(tBu2C6H2-1,4)].