Organometallic Early Lanthanide Clusters:  Syntheses and X-ray Structures of New Monocyclopentadienyl Complexes

The reaction of Ln(BH4)3(THF)3 or LnCl3(THF)3 with 1 equiv of KCp*‘ ligand (Cp*‘ = C5Me4n-Pr) afforded the new monocyclopentadienyl complexes Cp*‘LnX2(THF)n (X = BH4, Ln = Sm, n = 1, 1a, Ln = Nd, n = 2, 1b; X = Cl, Ln = Sm, n = 1, 3a) and [Cp*‘LnX2]n‘ (X = BH4, n‘ = 6, Ln = Sm, 2a, Ln = Nd, 2b; X = Cl, Ln = Nd, 4b). All these compounds were characterized by elemental analysis and 1H NMR. Crystals of mixed borohydrido/chloro-bridged [Cp*‘6Ln6(BH4)(12-x)Clx(THF)n‘] (x = 10, n‘ = 4, Ln = Sm, 2a‘, Ln = Nd, 2b‘; x = 5, n = 2, Ln = Sm, 2a‘ ‘) were also isolated. Compounds 2a, 2b, 2a‘, 2b‘, and 2a‘ ‘ were structurally characterized; they all exhibit a hexameric structure in the solid state containing the [Cp*3Ln3X5(THF)] building block. The easy clustering of THF adducts first isolated is illustrative of the well-known bridging ability of the BH4 group. Hexameric 2a was found to be unstable in the presence of THF vapors; this may be correlated to the opening of unsymmetrical borohydride bridges observed in the molecular structure.