RESUMEN
The syntheses and molecular structures of new SmII and TmII N,N-dimethylaminodiboranate (DMADB) complexes are described. Treating SmI2(THF)2 with Na(H3BNMe2BH3) in THF results in the formation of Sm(H3BNMe2BH3)2(THF)3 (1), which can be readily converted to Sm(H3BNMe2BH3)2(DME)2 (DME = 1,2-dimethoxyethane) or Sm(H3BNMe2BH3)2(diglyme) by exchange with the corresponding ether. We also show that Sm(H3BNMe2BH3)2(THF)3 can be prepared by reduction of the SmIII compound Sm(H3BNMe2BH3)3(THF) with KC8 and that addition of 18-crown-6 to this reaction mixture results in the formation of the SmII compound Sm(H3BNMe2BH3)2(18-crown-6). In a similar fashion, two new TmII complexes have been synthesized: treatment of TmI2 in THF with Na(H3BNMe2BH3) results in the formation of Tm(H3BNMe2BH3)2(THF)2 and Tm(H3BNMe2BH3)2(THF)3, which form a cocrystal. IR data and elemental analyses are reported for all the new compounds, as are their crystal structures. 1H and 11B NMR data are provided where available.
RESUMEN
The crystal structure of Th(BH4)4 is described. Two of the four BH4- ions are terminal and tridentate (κ3), whereas the other two bridge between neighboring ThIV centers in a κ2,κ2 (i.e., bis-bidentate) fashion. Thus, each thorium center is bound to six BH4- groups by 14 Th-H bonds. The six boron atoms describe a distorted octahedron in which the κ3-BH4- ions are mutually cis; the 14 ligating hydrogen atoms define a highly distorted bicapped hexagonal antiprism. The thorium centers are linked into a polymer consisting of interconnected helical chains wound about 4-fold screw axes. The structures of An(BH4)4 (An = Th, U) were also investigated by DFT. The geometries of [An(BH4)6]2-, [An3(BH4)16]4-, and [An5(BH4)26]6- fragments of the polymeric structures were optimized at the B3LYP and/or PBE levels. Most calculated geometries are 14-coordinate and agree with the experimental structures, but isolated [Th(BH4)6]2- units are predicted to feature 16-coordinate ThIV centers.