Synthesis, characterization and crystal structures of new difurylphosphido-bridged dinuclear ruthenium carbonyl complexes derived from ferrocenylacetylene ligands

The difurylphosphido-bridged dinuclear complex [Ru2(CO)6(μ-PFu2)(μ-η1,η2-Fu)] (Fu = 2-furyl) 1 readily reacts with two equivalents of each of the terminal alkynes HC = CR (R = Fc, p-C6H4Fc, p-C6H4NO2, Fc = Fe(η5-C5H5)(η5-C5H4)) by an interesting head-to-tail ynyl coupling with a furan group to form a series of phosphido-bridged diruthenium compounds containing a novel furyl-substituted C4hydrocarbyl chain of stoichiometry [Ru2(CO)4(μ-PFu2){μ-η1,η1, η2,η3-RCC(H)C(R)C(H)Fu}] (R = Fc 2, p-C6H4Fc 3, p-C6H4NO24) in moderate to good yields. Reaction of 1 with an equimolar amount of HC = CFc and HC= C(p-C6H4NO2) afforded a pair of isomers of [Ru2(CO)4(μ-PFu2){μ-η1, η1,η2,η3-R1CC(H)C(R2)C(H)Fu}] (R1= Fc, R2= p-C6H4NO25a; R1= p-C6H4NO2, R2= Fc 5b) together with a small mixture of 4. X-ray crystal structures of 2, 3, 5a and 5b are reported. All of these new alkyne-derived dinuclear complexes are electron precise with 34 cluster valence electrons in which the μ-η1,η2-furyl ligand acts as a three-electron donor and the μ-phosphido Ru2framework is retained in the products upon alkyne coupling reactions. The resulting organic fragment of each complex is coordinated to the Ru atoms via a π, a π-allyl and two σ bonds, and donates seven electrons to the metal core.