Treatment of [Ru2(μ-CO)(CO)4{μ-(RO)2PN(Et)P(OR)2}2] (R = Me or Pri), electron-rich derivatives of [Ru2(CO)9], with a twice molar amount of a silver(I) salt in aprotic, weakly co-ordinating solvents such as acetone, acetonitrile or benzonitrile leads to the formation of the solvento species [Ru2(CO)5(solvent)- {μ-(RO)2PN(Et)P(OR)2}2]2+. The structure of the benzonitrile derivative, [Ru2(CO)5(PhCN){μ-(PriO)2PN(Et)P(OPri)2}2](SbF6)2, has been established by X-ray crystallography. The acetone molecule in [Ru2(CO)5(acetone){μ- (RO)2PN(Et)P(OR)2}2]2+ is readily replaced by various nucleophiles to afford products of the type [Ru2(CO)5L{μ-(RO)2PN(Et)P(OR)2}2]2+, where L is a neutral ligand such as CO, Me2C6H3NC, PhCN, C5H5N, H2O, Me2S or SC4H8, [Ru2Y(CO)5{μ-(RO)2PN(Et)P(OR)2}2]2+, where Y- is an anionic ligand such as Cl-, Br-, I-, CN-, SCN-, MeCO2-, CF3CO2- or [Ru2(μ-Y)(CO)4{μ-(RO)2- PN(Et)P(OR)2}2]+ where Y- is an anionic ligand such as Cl-, Br-, I-, SPh-, S2CNEt2-, MeCO2- or CF3CO2-. © 1990.