The reaction of Ln(BH4)(3)(THF)(3) or LnCl(3)(THF)(3) with 1 equiv of KCpstar' ligand (Cp-star' = C(5)Me(4)n-Pr) afforded the new monocyclopentadienyl complexes Cp-star'LnX(2)(THF)(n) (X =BH4, Ln = Sm, n = 1, 1 a, Ln = Nd, n = 2, 1b; X = Cl, Ln = Sm, n = 1, 3a) and [Cp-star'LnX(2)](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 H-1 NMR. Crystals of mixed borohydrido/chloro-bridged [CPstar'(6)Ln(6)(BH4)((12-x))Cl-x(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(3)(star)Ln(3)X(5)(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.