Silyl reagents (Me3Si-X) efficiently transfer X to Ir(H)2F(PtBu2Ph)2

Me3Si-X reagents react to completion at 25 degrees C in a short time to convert Ir(H)(2)FL2 (L = (PBu2Ph)-Bu-t) to Ir(H)(2)XL2. This involves formation of Ir-O, Ir-N, Ir-I, Ir-S and Ir-C(sp) bonds. Products include some pi(2)-X ligands such as carboxylate and acetamide, NHC(O)CH3. The acetamide is shown to be pi(2) in the solid state and in solution, but readily rearranges, by a transition state with Ir-O bond cleavage, to effect site exchange of the two inequivalent hydrides. The same synthetic approach succeeds for the more crowded metallated species and these reactions are shown to fail when F is replaced by Cl in the iridium reagent. Unsaturation at Ir is suggested to be central to the mechanism of these F/X transposition reactions. (C) 1998 Elsevier Science S.A.