Synthesis of a Trivalent P ‐Chloro‐Dithienophosphole and Its Reactivity with Organometallic Reagents

P ‐chloro‐dithieno[3,2‐ b :2′,3′‐ d ]phosphole was synthesized and isolated from the reaction of an aminophosphole and HCl. Developed to act as a common starting material for P ‐functionalized phospholes, the compound exhibits a surprising reactivity by generating dimeric biphospholes. Despite this apparent sensitivity, when reacting with organolithium and Grignard reagents, a series of differently P ‐functionalized dithieno[3,2‐ b :2′,3′‐ d ]phospholes was accessible. Unexpectedly, organolithium reagents showed reduced reactivity with the chlorophosphole, limiting yields of the desired products due to the competing dimerization. Nonetheless, P ‐functionalized phospholes were isolated from reactions of the title compound with both Grignard and organolithium reagents in yields equivalent to, or higher, than by previous methods. A bithiophene‐bridged bisphosphole system was also successfully synthesized without the necessity of generating a bis(dichlorophosphino) reagent. Finally, the isolated P ‐functionalized phospholes were analyzed for their photophysical properties. In general, these compounds are strong absorbers in the UV/Vis range of the optical spectrum. The phospholes' emissions were consistent with several previously reported, however, with low quantum yields.