Metal-Free Addition/Head-to-Tail Polymerization of Transient Phosphinoboranes, RPH-BH2: A Route to Poly(alkylphosphinoboranes)

Mild thermolysis of Lewis base stabilized phosphinoborane monomers (RRPBH2NMe3)-R-1-P-2 (R-1,R-2=H, Ph, or tBu/H) at room temperature to 100 degrees C provides a convenient new route to oligo- and polyphosphinoboranes [(RRP)-R-1-P-2-BH2](n). The polymerization appears to proceed via the addition/head-to-tail polymerization of short-lived free phosphinoborane monomers, (RRP)-R-1-P-2-BH2. This method offers access to high molar mass materials, as exemplified by poly(tert-butylphosphinoborane), that are currently inaccessible using other routes (e.g. catalytic dehydrocoupling).