Synthetic, Electrochemical, DFT, and Synchrotron X-ray Charge-Density Studies on Oxo-centered Triruthenium Clusters Supported by Electron-Withdrawing Carboxylates

Abstract

We herein report the synthesis, characterizations, and synchrotron X-ray charge-density studies of oxo-centered triruthenium(II,III,III) clusters [Ru 3 O(CHCl 2 COO) 6 (py) 3 ] (1) and [Ru 3 O(CHCl 2 COO) 6 (CO)(py) 2 ] (2) (py = pyridine). Dichloroacetate was chosen for its large scattering factor of the Cl atom, and its electron-withdrawing nature results in significant stabilization of the targeted lower-valent Ru 3 II,III,III state in the cluster framework. Multipole analysis revealed that the difference in electron populations between two crystallographically independent Ru centers is small for 1 (Δ = 0.30 e) but large for 2 (Δ = 1.46 e). Remarkable differences between 1 and 2 are also found in their static deformation density maps; substantial local charge depletion was found around the central μ 3 O atom for 1, which is less pronounced for 2. According to the topological characterization of Ru−μ 3 O bonds associated with the bond critical point, bcp, the electron density, ρ bcp , is in the range of 0.79−0.89 e Å −3 , and the total energy density, H bcp , is in the range of −0.21 to −0.05 hartree Å −3 . These findings represent the first charge-density distribution analysis of mixed-valence multinuclear Ru complexes including comparison between 3d and 4d transition-metal systems.