Mononuclear ruthenium complexes containing two different phosphines in trans position: I. Synthesis and spectroscopic characterization

New mononuclear ruthenium complexes Ru(CO)2(Y)(Y′)(PnBu3)[P(p-XC6H4)3] (Y, Y′ = H, CH3COO; X = CH3O, CH3, H, F, Cl), all containing a PnBu3 in trans position to a triarylphosphinic ligand differently substituted in the para position, were synthesized. These ligands were chosen in order to change the basicity of the phosphine in trans to the PnBu3, without relevant steric changes. Spectroscopic data of the new complexes were correlated with the basicity of the triarylphosphines or with the mesomer effect of the substituent in the para position of the aromatic ring. The presence of two different phosphines into a mononuclear ruthenium complex seems an interesting model to study the “trans effect” for octahedral species.