Preparation of unsymmetrical diaryl selenides via SNAr reactions in η6-chloroarene transition metal complexes

Unsymmetrical diaryl selenides were prepared by nucleophilic displacement of chloride with areneselenolates in eta(6)-(arene) Cr(CO)(3), FeCpPF6, and Mn(CO)(3)PF6 complexes. Arene-selenolates were conveniently generated in situ by hydrazine reduction of the corresponding diaryl diselenides and reacted with chloroarene Cr(CO)3 complexes in dimethyl sulfoxide at 70 degrees C. The reactivity of the cationic FeCpPF6 and Mn(CO)(3)PF6 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 Se-77 NMR. As compared with the free diaryl selenide, complexation caused a 20-45 ppm downfield shift.