Ruthenium(II) complexes with chelated RCE2 − ions (E=O or S) bearing 1-(diphenylphosphino)-2-(2-pyridyl)ethane (ppye). Crystal structures of cis,trans-[Ru(RCO2)(ppye)2]PF6 (R=H or CH3)

The Ru(II) carboxylates c,t-[Ru(RCO2)(ppye)2]PF6 [ppye=1-(diphenylphosphino)-2-(2-pyridyl)ethane; R=H, CH3, CF3, cyclo-C6H11, and C6H5] have been prepared from c,t,c-[Ru(CH3CN)2(ppye)2](PF6)2 by reaction with RCO2Na salts. The complexes have been characterised in solution by multinuclear NMR, and the structure in the solid state for both acetate and formate has been determined by X-ray diffraction analysis. Complex c,t-[Ru(HCO2)(ppye)2]PF6 undergoes substitution of CO2 with CS2 affording c,t-[Ru(HCS2)(ppye)2]PF6, which is converted into the stable t,c via the c,c isomer. Complexes c,t-[Ru(RCS2)(ppye)2]PF6 [R=CH3CH2O or (CH3)2N] have also been prepared and characterised. Both species slowly isomerise into the stable c,c derivatives. A variable-temperature 1H NMR investigation has evidenced a fluxional behaviour in solution of all complexes of the type c,t-[Ru(RCE2)(ppye)2]PF6 (E=O or S), which is ascribable to a restricted rotation of phenyl rings of ppye. The protonation reaction of c,t-[Ru(CH3CO2)(ppye)2]+ has also been studied. Dicationic c,t-[RuL2(ppye)2]2+ complexes are formed when HBF4 is used in the presence of a coordinating solvent L [L=CH3CN or (CH3)2SO]. Conversely, carboxylic acids stronger than CH3CO2H react with c,t-[Ru(CH3CO2)(ppye)2]+ affording c,t-[Ru(RCO2)(ppye)2]+ complexes.