A new addition to the library of diorganoboranes available for functionalizing olefins and alkynes is reported. HB (C6F5) 2 can be prepared in multigram quantities from ClB (C6F5) 2 or B (C6F5) 3 using silanes as hydride transfer agents. The characteristics of HB (C6F5) 2 as a hydroboration reagent in comparison to other commonly employed reagents for this purpose are described in detail.