Versatile and highly efficient synthesis of diruthenium tetrahydride complex

• A diruthenium tetrahydride complex was efficiently synthesized by a simple procedure.
• Treatment of chloride complexes with NaOH in the presence of 2-propanol led to the introduction of hydrides.
• Salt metathesis followed by the β-hydrogen elimination of 2-propoxide is the key step of the formation of hydride.
• Various chloride complexes of Ru(II), Ru(III), and Ru(IV) can be used as a starting material.

A highly efficient and hydride reagent-free synthesis of diruthenium polyhydride cluster is reported. Salt metathesis followed by β-hydride elimination was the key reaction for introducing hydride. Heating Ru(III) complex, [Cp‡RuCl2]2 (2a, Cp‡ = 1,2,4-tri-tert-butylcyclopentadienyl), in 2-propanol in the presence of base afforded diruthenium tetrahydride complex, Cp‡Ru(μ-H)4RuCp‡ (1), in nearly quantitative yield. Ruthenium halide complexes of different oxidation states were also converted to 1 under the same condition. These results suggest that the reaction mechanism proceeds via the reduction of ruthenium halide complexes, followed by salt metathesis and β-hydride elimination, and then hydrogen transfer from 2-propanol.

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