Syntheses, characterization and structure determination of {[CpRu(X)] 2(η 2,μ 2-dppe) 2} complexes (X=Cl, N 3; dppe=Ph 2PCH 2CH 2PPh 2) : Chelating vs. bridging behavior of a classical bidentate ligand

Abstract

Phosphine substitution reactions between (η 5-C 5H 5)Ru(PPh 3) 2Cl ( 1) and 1,2-bis(diphenylphosphino)ethane (Ph 2P(CH 2) 2PPh 2, dppe), in refluxing benzene or in toluene at 80°C afforded a mixture of complexes where dppe behaves both as a bridging and as a chelating ligand. CpRu(η 2-dppe)Cl ( 2) and {[CpRu(Cl)] 2(η 2,μ 2-dppe) 2} ( 3) were separated by fractional precipitation from the reaction mother-liquor, and were characterized by 1H, 13C, 31P NMR, elemental analysis and IR spectroscopy. The ( 2):( 3) ratio in the composition of the reaction product was found to be independent of the reaction time. In solution and at room temperature, ( 3) exists in both boat and chair conformers of a 10-membered ring, while at lower temperatures, and in the solid-state, only the chair conformer is observed. Compounds ( 2) and ( 3) undergo halide-displacement upon reacting with NaN 3 in the presence of ethanol to yield CpRu(η 2-dppe)(N 3) ( 4) and {[CpRu(N 3)] 2(η 2,μ 2-dppe) 2} ( 5), respectively. The crystal structures of ( 3) and ( 5) were determined.