Ligand-Directed Metalation of a Gold Pyrazolate Cluster.

Solid "[Au]" (H = 3-[pyrid-2-yl]-5-butyl-1-pyrazole) can be crystallized as cyclic [Au(μ-)] and [Au(μ-)] clusters from different solvents. The crystalline tetramer contains a square Au core with an HT:TH:TH:HT arrangement of ligand substituents, which preorganizes the cluster to chelate to additional metal ions via its pendant pyridyl groups. The addition of 0.5 equiv of AgBF to [Au] yields [AgAu(μ-)][BF], where two edges of the Au square are spanned by Ag ions via metallophilic Ag···Au contacts. Treatment of [Au] with [Cu(NCMe)]PF affords the metalloligand helicate [CuAu(μ-)][PF], via oxidation of the copper and partial fragmentation of the cluster.