Inverse cycloheptatrienyl sandwich complexes of uranium and neodymium

Reaction of UX4 (X = NEt2 or BH4) with K[C7H9] afforded the anionic complexes K[X3U(mu-eta(7):eta(7)-C7H7)UX3] whereas treatment of [Nd(BH4)(3)(thf)(2)] (thf = tetrahydrofuran) with K[C7H9] gave the neutral compound [(thf)(BH4)(2)Nd(mu-eta(7):eta(7)-C7H7)Nd(BH4)(thf)(2)]. The formation of the cycloheptatrienyl ligand resulted from the disproportionation reaction 3 C7H9- --> C7H73- + 2 C7H10. The crystal structure of [(thf)(BH4)(2)Nd(mu-eta(7):eta(7)-C7H7)Nd(BH4)(thf)(3)], the first cycloheptatrienyl compound of a 4f element, has been determined.