Reaction of Ru₃(CO)₁₂ with Dibenzylideneacetone

The thermal reaction of Ru3(CO)12 with dibenzylideneacetone PhCHCHCOCHCHPh (1) was studied. From the solution, the trinuclear complexes Ru3(CO)6{μ3-η2-η2-η2-OC(CHCHPh)-CHCPh}2 (6) and Ru3(CO)7{η2-OC(CHCHPh)CHCPh}{μ-η-η4-O-C(CHCHPh)-CH-CPh-CH(CH2Ph)C(O)(CHCHPh)}{μ3-η-η-η4-(CH2Ph)CHC(O)-CHCHPh} (7) were isolated, and the precipitate was found to contain the tetranuclear complex Ru4(CO)8{μ3-η-η2-η6-O-C(CHCHPh)CH-CPh-CH(CH2Ph)-C(O)-CHCHPh}2 (8). The organic ligand in complexes realizes different coordination modes forming five-membered oxaruthenacycle, η3-coordinated dihydropyran cycle, η4-coordinated diene, or oxadiene fragments. Complex 7 is unstable and undergoes chemical transformations yielding complex 8. Reversible changes occur with complex 8 upon dissolution in acetone, and binuclear complex Ru2(CO)4(η-OCMe2)(μ-η-η2-η6-O-C(CHCHPh)CH-CPh-CH(CH2Ph)-C(O)-CHCHPh) (9) is formed. The central Ru2O2 cycle in complex 8 is cleaved and the formed vacant coordination site is occupied by an acetone molecule in complex 9. Complexes 6−9 were characterized by IR and 1H NMR spectroscopy, and their structures were determined by single-crystal X-ray diffraction analysis. The structural and spectroscopic features and possible pathways of the complexes' transformations are discussed.