Treatment of LnCl 3 (THF) x with one equivalent of Na 2 [nido-7,8-C 2 B 9 H 1 1 ] in THF gave the half-sandwich lanthanacarborane chloride compound (η 5 -C 2 B 9 H 1 1 )Ln(THF) 2 (μ-Cl) 2 Na(THF) 2 (Ln=Y (1), Er (2), Yb (3), Lu (4)). Recrystallization of 1 or 3 from a wet THF-toluene solution afforded the ionic compound [LnCl 2 (THF) 5 ][nido-C 2 B 9 H 1 2 ] (Ln=Y (5), Yb (6)). Reaction of 1 or 3 with Na 2 [nido-7,8-C 2 B 9 H 1 1 ] in a molar ratio of 1:1 in THF generated the full-sandwich lanthanacarborane {(η 5 -C 2 B 9 H 1 1 ) 2 Ln(THF) 2 }{Na(THF) 2 } (Ln=Y (7), Yb (8)). All of these new compounds were characterized by 1 H-, 1 3 C-, and 1 1 B-NMR spectra and elemental analyses. The solid-state structures of 5 and 6 were further confirmed by single-crystal X-ray analyses.