Extremely Electron-Rich, Boron-Functionalized, Icosahedral Carborane-Based Phosphinoboranes

We have prepared the first examples of B9-connected trivalent aryl and alkyl phosphinoborane species via Pd-catalyzed phosphination of 9-iodo-<i>meta</i>-carborane. Our studies highlight the unique electronic features of the B9-connected <i>meta</i>-carboranyl moiety as compared to its C1-based analogue. This work suggests that the B9-functionalized <i>meta</i>-carboranyl substituent in these ligands exhibits more electron-releasing character than any other known carbon-based substituent, ultimately laying the foundation for a new class of phosphine ligands with extremely electron-rich character