SILYL REAGENTS (ME3SI-X) EFFICIENTLY TRANSFER X TO IR(H)(2)F((PBU2PH)-BU-T)(2)

Me3Si-X reagents react to completion at 25 degrees C in a short time t o convert Ir(H)(2)FL2 (L = (PBu2Ph)-Bu-t) to Ir(H)(2)XL2. This involve s formation of Ir-O, Ir-N, Ir-I, Ir-S and Ir-C(sp) bonds. Products inc lude 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 solutio n, but readily rearranges, by a transition state with Ir-O bond cleava ge, to effect site exchange of the two inequivalent hydrides. The same synthetic approach succeeds for the more crowded metallated species a nd these reactions are shown to fail when F is replaced by Cl in the i ridium reagent. Unsaturation at Ir is suggested to be central to the m echanism of these F/X transposition reactions. (C) 1998 Elsevier Scien ce S.A.