Phosphinoboranes that combine bulky electron-rich phosphides and electron deficient B(C6F5)(2) fragments produce monomeric phosphinoboranes that undergo facile addition of H-2 to give the phosphine-borane adducts (R2PH)(HBR'(2)). This finding in combination with DFT calculations shed light on the uptake of H-2 across a group 13-group 15 bond, a critical requirement for the development of recyclable H-2 storage materials.