Protonation of diphosphazane ligand-bridged derivatives of diruthenium nonacarbonyl by protic acids with co-ordinating and non-co-ordinating conjugate bases

Abstract

Protonation of the diphosphazane ligand-bridged derivatives [Ru₂(µ-CO)(CO)₄{µ-(RO)₂PN(Et)P(OR)₂}₂](R = Me or Prⁱ) by HBF₄ or HPF₆ leads to the formation of the cationic hydrido products [Ru₂H(CO)₅{µ-(RO)₂PN(Et)P(OR)₂}₂]⁺ in which the hydride ligand is co-ordinated terminally. On the other hand protonation of these species with strong protic acids HA having conjugate bases A^– with co-ordinating properties [A^–= Cl^–, Br^–, NO₃^–, FB(O)OH^– or CF₃CO₂^–] gives rise to products of the type [Ru₂A(CO)₅{µ-(RO)₂PN(Et)P(OR)₂}₂]⁺ and/or [Ru₂(µ-A)(CO)₄{µ-(RO)₂PN(Et)P(OR)₂}₂]⁺. Weak acids HA (A^–= SPh^– or HCO₃^–) also afford these types of products but the presence of a strong acid such as HPF₆ is necessary. The structures of two of the products [Ru₂{µ-OB(F)OH}(CO)₄{µ-(PrⁱO)₂PN(Et)P(OPrⁱ)₂}₂]BF₄ and [Ru₂(µ-SPh)(CO)₄{µ-(MeO)₂PN(Et)P(OMe)₂}₂]PF₆ have been established by X-ray crystallography and are discussed as is the fluxional behaviour of the hydrido species [Ru₂H(CO)₅{µ-(RO)₂PN(Et)P(OR)₂}₂]⁺.