The borane B(C6F5)(3) is a precatalyst for H/D exchange between H-2 and deuterium-labeled silanes (D3SiPh, D2SiMePh, DSiMe2Ph, DSiEt3). Experimental and DFT studies reveal that B(C6F5)(3) itself cannot activate dihydrogen but converts to HB(C6F5)(2) under the action of hydrosilane. The latter species easily activates H-H and Si-H bonds by a sigma-bond metathesis mechanism, which was further confirmed by the reactions of BD3 center dot THF with H-2.