SYNTHESIS, SPECTROSCOPIC PROPERTIES AND CRYSTAL-STRUCTURES OF [ML(2)CL(2)] [M=TH OR U L=ETA-C5H3(SIME(3))(2)-1.3] AND [UL(2)X(2)] (X=BR, I OR BH4)

1,3-Bis(trimethylsilyl)cyclopentadienyl has been employed in the preparation of some actinocene(IV)halides and tetrahydridoborates. Crystal structure determinations of [M{C5H3(SiMe(3))(2)-1,3}Cl-2(2)] (M = Th or U) and [U{C5H3(SiMe(3))(2)-1,3}(2)X(2)] (X = Br or BH4) showed that these four complexes are isostructural, crystallising in the space group C2/c. The iodo derivative [U{C5H3-(SiMe(3))(2)-1,3}I-2(2)] crystallises in the chiral space group P2(1)2(1)2(1) in which the two cyclopentadienyl groups within the molecule are crystallographically distinct. Variable-temperature H-1 and B-11 NMR spectroscopic data for [U{C5H3(SiMe(3))(2)-1,3}(2)(BH4)(2)] and its thorium analogue revealed the presence of fluxional processes.