PO23- and AsO3-: Pnictogenide Ligands in the Highly Charged Re4 Cluster Anions [{Re4(PO)3(PO2)}(CN)12]8-, [{Re4As2(AsO)2}(CN)12]8-, and [{Re4(AsO)4}(CN)12]8.

New tetrahedral anionic rhenium cluster complexes [{Re4(PO)3(PO2)}(CN)12]8- (1) and [{Re4As2(AsO)2}(CN)12]8- (2) have been synthesized by the reaction of ReI3 with NaCN and Pred or KCN and Asgray, respectively. Compound 2 was further oxidized by aqueous H2O2 to produce the cluster anion [{Re4(AsO)4}(CN)12]8- (3). The anions contain new pnictogen/oxygen-based ligands, PO23- and AsO3-, which were stabilized by the coordination to the triangular faces of the tetrahedral Re4 metallocluster in μ3-mode. All three compounds were crystallized as either sodium or potassium salts, and their crystal structures were determined by single crystal X-ray diffraction analysis.