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.