CHLOROTRIS((HEXAMETHYLDISILYL)AMIDO)THORIUM(IV), AND (TETRAHYDROBORATO)TRIS((HEXAMETHYLDISILYL)AMIDO)THORIUM(IV) AND ((HEXAMETHYLDISILYL)AMIDO)URANIUM(IV) - CRYSTAL-STRUCTURE OF (TETRAHYDROBORATO)TRIS((HEXAMETHYLDISILYL)AMIDO)THORIUM(IV)

Reaction of sodium (hexamethyldisilyl)amide with thorium tetrachloride or uranium tetrachloride yields chlorotris-((hexamethyldisilyl)amido)thorium(IV) or -uranium(IV), respectively. The chloroamides of thorium or uranium react with dimethylmagnesium or methyllithium yielding the methyl derivatives MeTh[N(SiMe3)2]3 or MeU[N(SiMe3)2]3, respectively. The chloro compounds yield BH4M[N(SiMe3)2]3 upon reaction with lithium tetrahydroborate, where M is thorium or uranium. Infrared spectra of the tetrahydroborate derivatives suggest that BH4- is bonded in a tridentate fashion in both compounds, the metal atoms being six-coordinate. Single-crystal X-ray analysis of the thorium borohydride confirms the infrared result. The white BH4Th[N(Si(CH3))2]3 crystals are rhombohedral with cell dimensions ar=11.137 Å and α1=113.61°; the triply primitive hexagonal cell has ah=18.640 (3) Å, ch=8.604 (1) Å, V=2489 Å3, Z=3, and Dx=1.40 g/cm3, space group Rim. The structure was refined by full-matrix least squares to a conventional R factor of 0.031 for 1014 data. The Th atom is on a threefold axis 2.32 Å from three nitrogen atoms and 2.61 Å from the boron atom, a distance which represents a triple bridge bond between Th and B. The three (dimethylsilyl)amide ligands are disordered by a mirror plane parallel to the threefold axis. CH3Th[N(Si(CH3)3)2]3 is isomorphous with BH4Th[N(Si(CH3)3)2]3 with cell dimensions ah=18.68 (1) Å and ch=8.537 (6) Å. The diffraction data yielded f''=12.16±0.33 e for the imaginary scattering term for Th with Cu Kα radiation. © 1979, American Chemical Society. All rights reserved.