PO₂^3– and AsO^3–: 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–

Abstract

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, PO2 3– 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.

The Metaphosphite (PO2−) Anion as a Ligand

“…Cummins’ PO‐complex (Figure 1 d) stands out as a unique mononuclear example [12] . The only known PO 2 ‐containing cluster (Figure 1 c) features trianionic, side‐on bound hypophosphite (PO 2 3− ) [11b] . In contrast, authentic monometaphosphite (PO 2 − ) ligands, as phosphorous analogues of the common nitrite anion, remain elusive.…”

“…Figure 1 b), e.g., via oxygen atom transfer (OAT) reactions to (di-)phosphide ligands. [8,11] Cummins PO-complex (Figure 1 d) stands out as a unique mononuclear example. [12] The only known PO 2containing cluster (Figure 1 c) features trianionic, side-on bound hypophosphite (PO 2 3À ).…”