Diruthenium(I,I) saccharinate complexes: Synthesis, molecular structure, and evaluation as catalysts for carbenoid reactions of diazoacetates

The dinuclear ruthenium complexes [Ru2(μ-sac)2(CO)6] (1), [Ru2(μ-sac)2(CH3CN)2(CO)4] (3), [Ru2(μ-sac)2(CO)5(PPh3)] (4) and [Ru2(μ-sac)2(CO)4(PPh3)2] (5) as well as the tetranuclear ruthenium complex [Ru2(μ-sac)2(CO)5]2 (2) (sac = saccharinate, C7H4NO3S−) were synthesized starting from Ru3(CO)12 and saccharin. X-ray crystal structure analysis of 1, 3A × p-xylene, 4 × CH2Cl2 and 5 × 3CH2Cl2 showed that the Ru22+ core is bridged through the amidate moieties of the two saccharinate ligands, with a head–tail arrangement in complexes 1, 3A and 5, and a head–head arrangement in 4. For complex 3, an equilibrium mixture of the head–head regioisomer 3A and a second species 3b exists in solution. Complexes 1 and 2 are suitable catalysts for the cyclopropanation of nucleophilic alkenes (styrene, cyclohexene and 2-methyl-2-butene) with methyl diazoacetate.

Graphical abstractThe first dinuclear Ru(I,I) complexes with bridging saccharinate ligands ([Ru2(μ-sac)2(CO)4L2]n, L = CO, CH3CN, PPh3) have been prepared. XRD analysis revealed the existence of regioisomers with head–head and head–tail arrangement, respectively, of the sac ligands. Complexes 1 and 2 catalyze the cyclopropanation of nucleophilic alkenes with methyl diazoacetate in good to fair yields.Figure optionsDownload full-size imageDownload as PowerPoint slide