Ligand-Directed Metalation of a Gold Pyrazolate Cluster.

Solid "[Au L ]" (H L = 3-[pyrid-2-yl]-5- tert butyl-1 H -pyrazole) can be crystallized as cyclic [Au 3 (μ- L ) 3 ] and [Au 4 (μ- L ) 4 ] clusters from different solvents. The crystalline tetramer contains a square Au 4 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 4 to [Au L ] yields [Ag 2 Au 4 (μ 3 - L ) 4 ][BF 4 ] 2 , where two edges of the Au 4 square are spanned by Ag + ions via metallophilic Ag···Au contacts. Treatment of [Au L ] with [Cu(NCMe) 4 ]PF 6 affords the metalloligand helicate [Cu 2 Au 2 (μ- L ) 4 ][PF 6 ] 2 , via oxidation of the copper and partial fragmentation of the cluster.