Synthetic,\nElectrochemical, DFT, and Synchrotron X‑ray\nCharge-Density Studies on Oxo-centered Triruthenium Clusters Supported\nby Electron-Withdrawing Carboxylates

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