B-11 NMR SOLUTION STUDIES OF THE INTERACTIONS BETWEEN SMI2(TETRAHYDROFURAN)(X) AND NIDO-PENTABORANE(9) COMPOUNDS

The nature of the interactions between samarium(II) and the nido-octah ydropentaborate anion, NaB5H8, and neutral nido-pentaborane(9), B5H9, in THF solutions were investigated by B-11 NMR spectroscopy. In these studies, chemical shifts, B-11-H-1(t) coupling constants, spectral lin e widths and variable temperature data for the apical and basal [B5H8] (-1) resonances indicate that significant interactions occur between t he paramagnetic samarium center and the [B5H8](-1) cluster with signif icantly weaker interactions observed between the samarium(II) and the neutral nido-pentaborane(9) cage. The B-11 NMR spectral data for both pentaborane clusters were observed to depend linearly and solely on th e Sm(II) concentration in solution. A mechanism is proposed to account for these observations.