Phosphonium salts metal-bridged

A large number metal-bridged phosphonium salts have been synthesized and characterized by cyclic voltammetry49 58. With these coordinated compounds, the electrochemical features generally arise from the ionized species. For example, in the phosphonium salts shown in Table 10, the cyclic voltammetric reduction occurs from the anions. 

From the reaction of divalent, first-row hexaaqua transition metal ions and MS4 (M = Mo, W), [Co(MS4)2] and [Ni(MS4)2] can be isolated, typically as quaternary phosphonium salts. The [MS4] ions act as bidentate ligands to the divalent metal ion, but the coordination geometries are different - tetrahedral for Co and square planar for Ni. These compounds model, in a structurally well-defined way, sulfide-bridged Co-Mo and Ni-Mo interactions and may serve as references for such interactions in CoMoS and NiMoS phases. 

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