Syntheses, characterization and structure determination of {[CpRu(X)](2)(eta(2),mu(2)-dppe)(2)} complexes (X=Cl, N-3; dppe=Ph2PCH2CH2PPh2) - Chelating vs. bridging behavior of a classical bidentate ligand

Phosphine substitution reactions between (eta(5)C(5)H(5))Ru(PPh3)(2)Cl (1) and 1,2-bis(diphenylphosphino)ethane (Ph2P(CH2)(2)PPh2, dppe), in refluxing benzene or in toluene at 80 degrees C afforded a mixture of complexes wher e dppe behaves both as a bridging and as a chelating ligand. CpRu(eta(2)-dp pe)Cl (2) and {[CpRu(Cl)](2)(eta(2),mu(2)-dppe)(2)} (3) were separated by f ractional precipitation from the reaction mother-liquor, and were character ized by H-1,C-13, P-31 NMR, elemental analysis and IR spectroscopy. The (2) :(3) ratio in the composition of the reaction product was found to be indep endent of the reaction time. In solution and at room temperature, (3) exist s in both boat and chair conformers of a 10-membered ring, while at lower t emperatures, and in the solid-state, only the chair conformer is observed. Compounds (2) and (3) undergo halide-displacement upon reacting with NaN3 i n the presence of ethanol to yield CpRu(eta(2)-dppe)(N-3) (4) and {[CpRu(N- 3)](2)(eta(2).mu(2)-dppe)(2)} (5), respectively. The crystal structures of (3) and (5) were determined. (C) 1999 Elsevier Science Ltd. All rights rese rved.