The reactions of the divalent lanthanide metallocenes [Cp*(2)Ln(thf)(2)] (Cp* = eta(5)-C5Me5; Ln = Sm, Yb) with realgar (As4S4) gave the open cage tetrametallic complex [(Cp*Sm-2)(Cp*Sm)(3)AsS3(Cp*AsS2)(2)(thf)(3)] (1) or the trimetallic cage compound [(Cp*Yb)(3)As2S4(Cp*AsS2)(thf)(2)] (2), respectively, by reductive cleavage of the inorganic cage. As result of a Cp* transfer, the novel Cp*AsS22- anion is formed. Moreover, the As2S44- anion, which is bound in 2, is observed for the first time in coordination chemistry. Closed cage compounds are formed by either using bulkier ligands or a different As/S cage. The reaction of [Cp'''Sm-2] (Cp''' = (1,2,4-(t-Bu)(3)C5H2)) with As4S4 and the reaction of [Cp*Yb-2(thf)(2)] with dimorphite (As4S3) gave the closed 11-vertex cage clusters [(Cp'''Sm)(3)(AsS3)(2)] (3) and [(Cp*Yb)(3)(AsS3)(2)] (4), respectively. The reaction of 3 with [CuMes] resulted in the formation of the Sm/S/Cu cluster [(Cp'''Sm(thf))(4)Cu4S6] (5), in which the Sm atoms encapsulate a classical Cu4S68- cluster core. This is the first transition metal chalcogenide cluster encapsulated by f-elements. Alternatively, the endohedral cluster can thus be described as [Cu-4@{(Cp'''Sm(thf))(4)S-6}], in which a Cu-4 tetrahedron is encapsulated by the samarium sulfido cluster {(Cp'''Sm(thf))(4)S-6}.