Synthesis and property of diruthenium complexes containing bridging cyclic diene ligands and the reaction of diruthenium tetrahydrido complex with benzene forming a μ-η~2:η~2-cyclohexadiene complex via partial hydrogenation on a Ru_2 center

摘要

The syntheses, structures, and reactivities of diruthenium complexes having a five-, six-, and seven-membered cyclic diene ligands are discussed in this paper. While the μ-η~2:η~2-cyclohexadiene complex 3 was readily prepared by the reaction of the diruthenium tetrahydrido complex 1 with 1,3-cyclohexadiene, 3 was alternatively synthesized by the reaction of 1 with benzene via partial hydrogenation of benzene on a diruthenium plane. While the μ-η~2:η~2-cyclohexadiene ligand was liberated as benzene upon mild heating, the treatment of 3 with ~tBuNC and CO caused further migration of hydrido ligand to the C_6 moiety to yield the μ-η~2-cyclohexenyl complex 6 and the μ-cyclohexylidene complex 8, respectively. The reactions of 1 with cyclopentadiene and cycloheptatriene also afforded the bridging cyclic diene complexes 10 and 11. While the thermolysis of the μ-η~2:η~2- cyclopentadiene complex 10 resulted in the degradation of the cluster skeleton forming Cp*RuCp (12), the μ-η~2:η~2- cycloheptadiene complex 11 was stable upon heating. These differences can be attributed to the aromatization of the cyclic diene moiety.