Reactivity of [Ru₂(CO)₆(μ-PFu₂)(μ- η¹,η²-Fu)] (Fu = 2-furyl) towards diphosphanes - Substitution, polymerisation, cyclometallation and elimination reactions

Thermal reaction of [Ru2(CO)6(μ-PFu2)(μ- η1,η2-Fu)] (Fu = 2-furyl) (1) with bis(diphenylphosphanyl)methane (dppm), bis(diphenylphosphanyl)amine (dppam), or bis(diphenylphosphanyl)methylamine (dppma), produces the substitution products [Ru2(CO)4(μ-PFu2)(μ-η1, η2-Fu)(μ-L)] [2 (L = dppm), 3 (L = dppam), 4 (L = dppma)] in good yields. The Ru-Ru edge is bridged by the diphosphane in each case, while the μ-η1,η2-bound furyl fragment remains intact. When the reactions were carried out using bis (diphenylphosphanyl) ethane (dppe) or bis(diphenylphosphanyl)propane (dppp), the compounds [Ru2(CO)5(μ-PFu2)(μ- η1-C6H4PPh (CH2)nPPh2)] [5 (n = 2), 6 (n = 3)] were isolated as the thermodynamic products in which both P atoms chelate to one Ru centre to afford five-(for 5) and six-membered (for 6) ruthenacycles, accompanied by orthometallation of one of the phenyl rings of the phosphane ligand. Interestingly, elimination of the coordinated furyl moiety occurs during the formation of 5 and 6. Upon reaction with bis (diphenylphosphanyl) butane (dppb), bis(diphenylphosphanyl)pentane (dpppe), or bis(diphenylphosphanyl)ferrocene (dppf), cyclometallation is not favoured in each case. Instead, [{Ru2(CO)5(μ-PFu2) (μ-η1,η2-Fu)}2(L)] [7a (L = dppb), 8a (L = dpppe), 9a (L = dppf)] and polymeric [Ru2(CO)4(μ-PFu2) (μ-η1,η2-Fu)(L)]n[7b (L = dppb), 8b (L = dpppe), 9b (L = dppf)] were obtained with the product yield depending on the stoichiometry of the reactants. All these new diruthenium complexes are electron-precise with 34 cluster valence electrons.