Reaction of [Ru3(CO)12] with tri(2-furyl)phosphine: Di- and tri-substituted triruthenium and phosphido-bridged diruthenium complexes

Reaction of [Ru3(CO)12] with tri(2-furyl)phosphine, P(C4H3O)3, at 40 °C in the presence of a catalytic amount of Na[Ph2CO] furnishes two triruthenium complexes [Ru3(CO)10{P(C4H3O)3}2] (1) and [Ru3(CO)9{P(C4H3O)3}3] (2) with the ligand coordinated through the phosphorus atom. Treatment of 1 and 2 with Me3NO at 40 °C affords the dinuclear phosphido-bridged complexes [Ru2(CO)6(μ-η1,η2-C4H3O){μ-P(C4H3O)2}] (3) and [Ru2(CO)5(μ-η1,η2-C4H3O){μ-P(C4H3O)2}{P(C4H3O)3}] (4), respectively, that are formed via phosphorus–carbon bond cleavage of a coordinated phosphine followed by coordination of the dissociated furyl moiety to the diruthenium center in a σ,π-alkenyl mode. Reaction of [Ru3(CO)12] with tri(2-furyl)phosphine in refluxing benzene gives, in addition to 3 and 4, low yields of the cyclometallated complex [Ru3(CO)9{μ-η1,η1-P(C4H3O)2(C4H2O)}2] (5). Treatment of 3 with EPh3 (E = P, As, Sb) at room temperature yields the monosubstituted derivatives [Ru2(CO)5(μ-η1,η2-C4H3O){μ-P(C4H3O)2}(EPh3)] (E = P, 8; E = As, 9; E = Sb, 10). Similar reactions of 3 with P(C4H3O)3, P(OMe)3 and ButNC yield 4, [Ru2(CO)5(μ-η1,η2-C4H3O){μ-P(C4H3O)2}{P(OMe)3}] (11) and [Ru2(CO)5(μ-η1,η2-C4H3O){μ-P(C4H3O)2}(NCBut)] (12), respectively. The molecular structures of complexes 3, 4 and 8 have been elucidated by single crystal X-ray diffraction studies. Each complex contains a bridging σ,π-alkenyl group and while in 4 the phosphine is bound to the σ-coordinated metal atom, in 8 it is at the π-bound atom. Protonation of 3 and 4 gives the hydride complexes [(μ-H)Ru2(CO)6(μ-η1,η2-C4H3O){μ-P(C4H3O)2}]+ (6) and [(μ-H)Ru2(CO)5(μ-η1,η2-C4H3O){μ-P(C4H3O)2}{P(C4H3O)3}]+ (7), respectively, while heating 3 with dimethylacetylenedicarboxylate (DMAD) in refluxing toluene gives the cyclotrimerization product, C6(CO2Me)6.