Treatment of Cp 3 Ln (Ln=Pr, Nd) with an equimolar amount of the Schiff base bis(acetylacetone)ethylenediamine (H 2 acacen) half hydrate (H 2 L 1 ·1/2H 2 O) or bis(salicylidene)trimethylenediamine (H 2 saltn) half hydrate (H 2 L 2 ·1/2H 2 O) in THF affords three novel μ-hydroxo-bridged tetranuclear organolanthanide complexes [η 5 -CpLn 2 L 2 (μ-OH)] 2 ·nTHF, L=L 1 , n=4, Ln=Pr (1), Nd (2); L=L 2 , n=2, Ln=Nd (3). A reaction scheme was proposed in which the cyclopentadienyl lanthanide coordination motif [CpLnL] (A) and the hydroxyl lanthanide motif [LnL(OH)] (B) cross-reacted and then dimerized through the μ-hydroxo bridges to give the tetranuclear Ln complexes containing an Ln 4 O 8 skeleton with two reciprocally oriented face-sharing defect cubanes. In each monomeric species [CpLn 2 L 2 (OH)] (C) the Ln atoms are 8- or 9-coordinated. All complexes have been characterized by EA, IR and Mass spectroscopy.