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

Tetramethylaluminato/halogenido(X) ligand exchange reactions in half-sandwich complexes [Cp La(AlMe ) ] are feasible in non-coordinating solvents and provide access to large coordination clusters of the type [Cp LaX ] . Incomplete exchange reactions generate the hexalanthanum clusters [Cp La X (AlMe ) ] (Cp =Cp*=C Me , X=I; Cp =Cp'=C H SiMe , X=Br, I). Treatment of [CpLa(AlMe ) ] with two equivalents Me SiI gave the nonalanthanum cluster [CpLaI ] , while the exhaustive reaction of [Cp'La(AlMe ) ] with the halogenido transfer reagents Me GeX and Me 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 ] and [Cp'LaX ] (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) Cp' La I ] and the heteroaluminato derivative [Cp' La Br (AlBr Me ) ]. The use of the Cp' ancillary ligand facilitates cluster characterization by means of NMR spectroscopy.