The Effect of N-Donor Ligands on the Reaction of Ruthenium Hydrides with 1-Alkynes

Abstract

Neutral ruthenium hydrides Ru(CO)ClH(L)(PPh3)2 bearing one N-donor ligand react with 1-alkynes at 23 °C to yield neutral alkenyl complexes Ru(CO)Cl(CHCHR)(L)(PPh3)2. Under similar conditions, cationic hydrido complexes [Ru(CO)H(L)2(PPh3)2]PF6 with pyridine-type N-donor ligands yield alkynyl complexes [Ru(CO)(CH≡CHR)(L)2(PPh3)2]PF6 as a result of the reaction of the intermediate labile alkenyl with a second molecule of alkyne. Under more forcing conditions, 1-alkynyl complexes could also be prepared from the neutral ruthenium hydrides. Cationic ruthenium hydrides with bidentate N-donor ligands are unreactive toward 1-alkynes. Neutral alkenyl complexes Ru(CO)Cl(CHCHR)(L)(PPh3)2 (R = p-MeC6H4, CMe3; L = pyridine, isoquinoline) reacted smoothly with 1-alkynes to afford the corresponding σ-alkynyl ruthenium derivatives Ru(CO)Cl(C≡CR)(L)(PPh3)2.