10.1021/jacs.9b10320.s001 Jaruwan Amtawong Jaruwan Amtawong David Balcells David Balcells Jarett Wilcoxen Jarett Wilcoxen Rex C. Handford Rex C. Handford Naomi Biggins Naomi Biggins Andy I. Nguyen Andy I. Nguyen R. David Britt R. David Britt T. Don Tilley T. Don Tilley Isolation and Study of Ruthenium–Cobalt Oxo Cubanes Bearing a High-Valent, Terminal Ru<sup>V</sup>–Oxo with Significant Oxyl Radical Character American Chemical Society 2019 EPR OAc Co II Co 3 O 4 Natural bond Ru V chemical properties cubane cluster reactive nature oxo cubane oxidizes assembly reaction Significant oxyl oxo cubane cubane core H 2 O 3 cubane pyridyl ligand non-negligible covalency oxidation chemistry isolable μ- oxo bis-cubane DFT studies electron-donating ability Co sites trityl radicals III ENDOR π- electron donation 2019-12-05 16:41:40 Dataset https://acs.figshare.com/articles/dataset/Isolation_and_Study_of_Ruthenium_Cobalt_Oxo_Cubanes_Bearing_a_High-Valent_Terminal_Ru_sup_V_sup_Oxo_with_Significant_Oxyl_Radical_Character/11323904 High-valent Ru<sup>V</sup>–oxo intermediates have long been proposed in catalytic oxidation chemistry, but investigations into their electronic and chemical properties have been limited due to their reactive nature and rarity. The incorporation of Ru into the [Co<sub>3</sub>O<sub>4</sub>] subcluster via the single-step assembly reaction of Co<sup>II</sup>(OAc)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub> (OAc = acetate), perruthenate (RuO<sub>4</sub><sup>–</sup>), and pyridine (py) yielded an unprecedented Ru­(O)­Co<sub>3</sub>(μ<sub>3</sub>-O)<sub>4</sub>(OAc)<sub>4</sub>(py)<sub>3</sub> cubane featuring an isolable, yet reactive, Ru<sup>V</sup>–oxo moiety. EPR, ENDOR, and DFT studies reveal a valence-localized [Ru<sup>V</sup>(<i>S</i> = 1/2)Co<sup>III</sup><sub>3</sub>(<i>S</i> = 0)O<sub>4</sub>] configuration and non-negligible covalency in the cubane core. Significant oxyl radical character in the Ru<sup>V</sup>–oxo unit is experimentally demonstrated by radical coupling reactions between the oxo cubane and both 2,4,6-tri-<i>tert</i>-butylphenoxyl and trityl radicals. The oxo cubane oxidizes organic substrates and, notably, reacts with water to form an isolable μ-oxo bis-cubane complex [(py)<sub>3</sub>(OAc)<sub>4</sub>Co<sub>3</sub>(μ<sub>3</sub>-O)<sub>4</sub>Ru]–O–[RuCo<sub>3</sub>(μ<sub>3</sub>-O)<sub>4</sub>(OAc)<sub>4</sub>(py)<sub>3</sub>]. Redox activity of the Ru<sup>V</sup>–oxo fragment is easily tuned by the electron-donating ability of the distal pyridyl ligand set at the Co sites demonstrating strong electronic communication throughout the entire cubane cluster. Natural bond orbital calculations reveal cooperative orbital interactions of the [Co<sub>3</sub>O<sub>4</sub>] unit in supporting the Ru<sup>V</sup>–oxo moiety via a strong π-electron donation.