Structure and properties of tris(quinoxaline-2,3-dithiolato)molybdate(IV)

Abstract

The synthesis, crystal structure, spectroscopic and electrochemical properties of tris(quinoxaline-2,3-dithiolato)molybdate(IV), [Mo(qdt)₃]^2–, are reported. [PPh₄]₂[Mo(qdt)₃]·H₂O crystallizes in the space group P2₁/c, with a= 20.150(20), b= 14.014(5), c= 23.530(20)Å, β= 104.34(8)°, and Z= 4. The anion has an essentially trigonal prismatic MoS₆ core with Mo–S (average) 2.393(10)Å. [Mo(qdt)₃]^2– undergoes reversible protonation on the ligand nitrogen atoms and the triply protonated species, formulated as [Mo(Hqdt)₃]⁺, has been isolated and characterized as its chloride salt. Cyclic voltammetry indicates that [Mo(qdt)₃]^2– undergoes one-electron reduction and oxidation processes. The oxidation product, [Mo(qdt)₃]^–(e.s.r. parameters g= 2.002, Ā= 32.9), can be generated in solution by chemical oxidation.