Nanoscale Organolanthanum Clusters: Nuclearity‐Directing Role of Cyclopentadienyl and Halogenido Ligands

Tetramethylaluminato/halogenido(X) ligand exchange reactions in half‐sandwich complexes [Cp(R)La(AlMe(4))(2)] are feasible in non‐coordinating solvents and provide access to large coordination clusters of the type [Cp(R)LaX(2)](x). Incomplete exchange reactions generate the hexalanthanum clusters [Cp(R) (6)La(6)X(8)(AlMe(4))(4)] (Cp(R)=Cp*=C(5)Me(5), X=I; Cp(R)=Cp′=C(5)H(4)SiMe(3), X=Br, I). Treatment of [Cp*La(AlMe(4))(2)] with two equivalents Me(3)SiI gave the nonalanthanum cluster [Cp*LaI(2)](9), while the exhaustive reaction of [Cp′La(AlMe(4))(2)] with the halogenido transfer reagents Me(3)GeX and Me(3)SiX (X=I, Br, Cl) produced a series of monocyclopentadienyl rare‐earth‐metal clusters with distinct nuclearity. Depending on the halogenido ion size the homometallic clusters [Cp′LaCl(2)](10) and [Cp′LaX(2)](12) (X=Br, I) could be isolated, whereas different crystallization techniques led to the aggregation of clusters of distinct structural motifs, including the desilylated cyclopentadienyl‐bridged cluster [(μ‐Cp)(2)Cp′(8)La(8)I(14)] and the heteroaluminato derivative [Cp′(10)La(10)Br(18)(AlBr(2)Me(2))(2)]. The use of the Cp′ ancillary ligand facilitates cluster characterization by means of NMR spectroscopy.