Efficient Synthesis of Ruthenium(II) η⁵-Dienyl Compounds Starting from Di-μ-chlorodichloro- bis[(1−3η:6−8η)-2,7-dimethyloctadienediyl]diruthenium(IV). Versatile Precursors for Enantioselective Hydrogenation Catalysts

Abstract

The dimeric complex di-μ-chlorodichloro-bis[(1−3η:6−8η)-2,7-dimethyloctadienediyl]diruthenium(IV) in the presence of base reacts with cyclic and acyclic dienes to the corresponding bis(η5-dienyl)ruthenium(II) compounds. Crystalline yellow compounds have been isolated in high yields for dienyl = cyclopentadienyl, pentamethylpentadienyl, cycloheptadienyl, indenyl, dimethylpentadienyl, and trimethylpentadienyl. The analogous reaction of cyclohexa-1,3-diene gives the ruthenium(0) compound (η6-benzene)(η4-cyclohexa-1,3-diene)ruthenium. The “open” bis(dienyl)ruthenium complexes can be converted into half-sandwich complexes through protonation and subsequent ligand exchange. These compounds can be used as precursors for efficient enantioselective hydrogenation catalysts.