Structural dynamics and ligand mobility in carboxylate and dithiocarbamate complexes of Ru(II) containing 1,1′-bis(diphenylphosphino)ferrocene (dppf)

Ruthenium(II) carboxylate and dithiocarbamate complexes containing 1,1′-bis(diphenylphosphino)ferrocene (dppf) were synthesized by displacement of triphenylphosphine in Ru(RCOO)2(PPh3)2 (R=Me, Et, Ph) and Ru(SC(S)NEt2)2(PPh3)2 with dppf. The complexes Ru(RCOO)2(dppf) (1a: R=Me, 1b: R=Et, 1c: R=Ph) and Ru(SC(S)NEt2)2(dppf) (3) were obtained in yields of 78–93%. The crystal structures of these complexes show coordination of the phosphorus atoms of dppf and four oxygen/sulphur atoms of carboxylate/dithiocarbamate ligands to a Ru(II) centre with axial-bond-distorted octahedral geometry. Two pseudo-polymorphic forms of 1c were isolated and crystallographically characterized. VT-1H- and 31P{1H}-NMR spectral studies of 1a–c and 3 demonstrate mono- and bidentate exchange behaviour of the carboxylate or dithiocarbamate ligands, together with concerted twisting of the Cp rings of the dppf ligand. Complex 1c in CH3CN at room temperature gives Ru(PhCOO)2(dppf)(CH3CN)(H2O) (2), the crystal structure of which reveals two monodentate benzoate ligands around octahedral ruthenium and intramolecular inter-ligand H-bonding interaction between the coordinated H2O and the pendant carboxylate oxygen atoms. The interrelationship of crystallographic properties, structural dynamics, ligand mobility and chemical instability of these complexes will be described.