Realgar as a Building Block for Lanthanide Clusters: Encapsulation of a Copper Cluster by a Lanthanide Cluster

The
reactions of the divalent lanthanide metallocenes [Cp*2Ln­(thf)2] (Cp* = η5-C5Me5; Ln = Sm, Yb) with realgar (As4S4)
gave the open cage tetrametallic complex [(Cp*2Sm)­(Cp*Sm)3AsS3(Cp*AsS2)2(thf)3] (1) or the trimetallic cage compound [(Cp*Yb)3As2S4(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‴2Sm] (Cp‴
= (1,2,4-(t-Bu)3C5H2)) with As4S4 and the reaction of [Cp*2Yb­(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))4Cu4S6] (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 [Cu4@{(Cp‴Sm­(thf))4S6}],
in which a Cu4 tetrahedron is encapsulated by the samarium
sulfido cluster {(Cp‴Sm­(thf))4S6}.