Reaction of [Ru-3(CO)(12)] with tri(2-furyl)phosphine: Di- and tri-substituted triruthenium and phosphido-bridged diruthenium complexes

Reaction of [Ru-3(CO)(12)] with tri(2-furyl)phosphine, P(C4H3O)(3), at 40 degrees C in the presence of a catalytic amount of Na[Ph2CO] furnishes two triruthenium complexes [Ru-3(CO)(10){P(C4H3O)(3)}(2)] (1) and [Ru-3(CO)(9){P(C4H3O)(3)}(3)] (2) with the ligand coordinated through the phosphorus atom. Treatment of 1 and 2 with Me3NO at 40 degrees C affords the dinuclear phosphido-bridged complexes [Ru-2(CO)(6)(mu-eta(1),eta(2)-C4H3O){mu-P(C4H3O)(2)}] (3) and [Ru-2(CO)(5)(mu-eta(1),eta(2)-C4H3O){mu-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 sigma,pi-alkenyl mode. Reaction of [Ru-3(CO)(12)] with tri(2-furyl) phosphine in refluxing benzene gives, in addition to 3 and 4, low yields of the cyclometallated complex [Ru-3(CO)(9){mu-eta(1),eta(1)-P(C4H3O)(2)(C4H2O)}(2)] (5). Treatment of 3 with EPh3 (E = P, As, Sb) at room temperature yields the monosubstituted derivatives [Ru-2(CO)(5)(mu-eta(1),eta(2)-C4H3O){mu-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 (BuNC)-N-t yield 4, [Ru-2(CO)(5)(mu-eta(1),eta(2)-C4H3O){mu-P(C4H3O)(2)}{P(OMe)(3)}] (11) and [Ru-2(CO)(5)(mu-eta(1),eta(2)-C4H3O){mu-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 sigma,pi-alkenyl group and while in 4 the phosphine is bound to the sigma-coordinated metal atom, in 8 it is at the pi-bound atom. Protonation of 3 and 4 gives the hydride complexes [(mu-H)Ru-2(CO)(6)(mu-eta(1),eta(2)-C4H3O){mu-P(C4H3O)(2)}](+) (6) and [(mu-H)Ru-2(CO)(5)(mu-eta(1),eta(2)-C4H3O){mu-P(C4H3O)(2)}{P(C4H3O)(3)}] (+) (7), respectively, while heating 3 with dimethylacetylenedicarboxylate (DMAD) in refluxing toluene gives the cyclotrimerization product, C-6(CO2Me)(6).