Contrasting pathways for the reactions of the electron-acceptor ligands tetrachloro-1,2- and -1,4-benzoquinone with the diruthenium diphosphazane-bridged derivatives [Ru 2 (µ-CO)(CO) 4 {µ-(RO) 2 PN(Et)P(OR) 2 } 2 ](R = Me or Pr i )

Treatment of [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) with o-chloranil leads to electron transfer and the fission of one of the diphosphazane ligands to form [Ru2{µ-(RO)2PN(Et)C(O)}{(RO)2POC6Cl4O}(CO)4{µ-(RO)2PN(Et)P(OR)2}], characterized by X-ray crystallography for R = Me, and found to contain a chelating (MeO)2POC6Cl4O group and a novel bridging ligand derived by the coupling of a (RO)2PN(Et) fragment to a co-ordinated carbonyl group; in contrast, reaction with p-chloranil gives the radical anion salt [Ru2Cl(CO)5{µ-(RO)2PN(Et)P(OR)2}2][p-OC6Cl4O] resulting from the p-chloranil functioning as a chlorinating agent as well as an electron acceptor.