Uranium(IV) amide and halide derivatives of two tripodal tris(N-arylamido-dimethylsilyl)methanes

Reaction of three equivalents of ArNH2 (Ar = 3,5-Me2C6H3) with HC(SiMe2Br)(3) in the presence of the auxiliary base NEt3 afforded the tripodal tris(N-arylamine-dimethylsilyl)methane HC{SiMe2N(H)Ar}(3) (1) in 83% yield. Three-fold deprotonation of 1 with n-butyllithium afforded the corresponding tri-lithium tris(N-arylamido-dimethylsilyl)methane etherate [HC{SiMe2N(Li) Ar}(3)(OEt2)] (2) in 92% yield. Salt elimination reactions between 2 or the known complex [HC{SiMe2N(Li)Ar'}(3)(OEt2)(2)] (3) (Ar' = 4-MeC6H4) with one equivalent of uranium(IV) tetrachloride afforded the corresponding tris(N-arylamido-dimethylsilyl) methane uranium(IV) chloride complexes as monomeric [U(Cl){HC(SiMe2NAr)(3)}(THF)] (4) and dinuclear [{HC(SiMe2NAr')(3)} U(Cl)(mu-Cl)U(THF)(2){(Ar'NSiMe2)(3)CH}] (5) species in 70 and 90% crystalline yields, respectively. Treatment of 4 and 5 with one equivalent of trimethylsilyl iodide resulted in halide exchange and formation of [U(I){HC(SiMe2NAr)(3)}(THF)(2)] (6) and [U(I){HC(SiMe2NAr')(3)}(THF)] (7) in 85 and 90% yields, respectively. The heteroleptic amide [U(NCy2){HC(SiMe2NAr)(3)}(THF)] (8) was prepared from the reaction between 4 and one equivalent of lithium dicyclohexylamide and was isolated in 78% yield. Analogous attempts to prepare [U(NCy2){HC(SiMe2NAr')(3)}(THF)] (9) from 5 consistently resulted in intractable mixtures of products. Complexes 1-8 have been characterised by X-ray crystallography, NMR spectroscopy, FTIR spectroscopy, room temperature Evans method solution magnetic moments, and CHN micro-analyses.