Preparation of Unsymmetrical Diaryl Selenides via S<sub>N</sub>Ar Reactions in η<sup>6</sup>-Chloroarene Transition Metal Complexes

Unsymmetrical diaryl selenides were prepared by nucleophilic displacement of chloride with areneselenolates in η<sup>6</sup>-(arene) Cr(CO)<sub>3</sub>, FeCpPF<sub>6</sub>, and Mn(CO)<sub>3</sub>PF<sub>6</sub> complexes. Areneselenolates were conveniently generated in situ by hydrazine reduction of the corresponding diaryl diselenides and reacted with chloroarene Cr(CO)<sub>3</sub> complexes in dimethyl sulfoxide at 70 °C. The reactivity of the cationic FeCpPF<sub>6</sub> and Mn(CO)<sub>3</sub>PF<sub>6</sub> chloroarene complexes was substantially higher, affording substitution products at ambient temperature in ethanol with areneselenolates generated by sodium borohydride reduction. Intermediate (arylseleno)arene chromium and iron complexes were isolated and characterized by <sup>77</sup>Se NMR. As compared with the free diaryl selenide, complexation caused a 20−45 ppm downfield shift.