Bis(pentamethylcyclopentadienyl) complexes of cerium(III). Crystal structure of (C5Me5)2CeCH(SiMe3)2

CeCl3.xTHF (1 < x < 2) reacts with 2 equiv of Cp*Li in THF forming Cp*2CeCl2Li(THF)2.5 (1). The coordinated THF can easily be displaced by DME to form Cp*2CeCl2Li(DME) (2). When 1 is heated to 250 °C (0.01 mmHg), (Cp*2CeCl)n (4) sublimes. A number of adducts, Cp*2CeCl·L, (5, L = THF, n = 1; 6, L = t-BuCN, n = 2), are accessible starting from 4. Metathesis of 4 with LiCH(SiMe3)2 and NaN(SiMe3)2 in toluene gives Cp*2CeCH(SiMe3)2 (8) and Cp*2CeN(SiMe3)2 (11), respectively, Compound 8 reacts with LiCl in the presence of TMEDA to form Cp*2CeCl2Li(TMEDA)2 (3) and LiCH(SiMe3)2. Addition of t-BuCN to 8 affords the adduct Cp*2CeCH(SiMe3)2·t-BuCN (9). (Cp*2CeH)2 (10) can be made by hydrogenolysis of 8 under mild conditions. Cp*2CeNH-t-Bu·NH2-t-Bu (12) and also 11 are prepared by the reaction of 8 with the corresponding amines. 8 crystallizes in the monoclinic space group P21/n with a = 11.061 (3) Å, b = 23.46 (1) Å, c = 11.692 (5) Å, and β = 102.99 (2)° (Z = 4). Least-squares refinement leads to a final R (based on F) of 0.038 for 5534 independent reflections. The molecular structure consists of monomeric Cp*2CeCH(SiMe3)2 units with a bent sandwich configuration. The average (ring centroid)-Ce-(ring centroid) angle is 134°. The CH(SiMe3)2 fragment is coordinated in a highly unsymmetrical fashion with a Ce-C σ-bond distance of 2.536 (5) Å.