Electron-deficient organouranium chemistry: Synthesis and reactivity of monocyclopentadienyldiphenylphosphidouranium trisborohydrides [C(5)R(4)PPh(2)U(BH4)(3)] (R=H or CH3) and of their borane adducts

The reactivity of the monocyclopentadienyl complex [(C(5)H(4)PPh(2))U(BH4)(3)] and of its borane adduct [(C(5)H(4)PPh(2) . BH3)U(BH4)(3)] strongly suggest that in solutions these complexes are in equilibrium with the biscyclopentadienyls [(C(5)H(4)PPh(2))(2)U(BH4)(2)] and [(C(5)H(4)PPh(2) . BH4)(2)U(BH4)(2)] and uranium tetraborohydride [U(BH4)(4)] which is the most reactive species in such systems. Both rearrange in the presence of neutral ligands and are only characterizable in solution. The analogue tetramethylcyclopentadienyl [(C(5)Me(4)PPh(2) . BH3)U(BH4)(3)] a model of monolinked dimetallics, is stable and has been isolated.