NDLI: The influence of reversible trianionic pincer $OCO^{3−}μ-oxo$ $Cr^{IV}$ dimer formation $([Cr^{IV}]_{2}(μ-O))$ and donor ligands in oxygen-atom-transfer (OAT)

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	O'reilly, Matthew E. Veige, Adam S. Del Castillo, Trevor J. Abboud, Khalil A.
Description	Author Affiliation: O'Reilly ME ( University of Florida, Department of Chemistry, Center for Catalysis, P.O. Box 117200, Gainesville, Florida 32611, USA.)
Abstract	The oxygen-atom-transfer (OAT) from $[^{t}BuOCO]Cr^{V}(O)(THF)$ (2) (where $^{t}BuOCO$ = $[2,6-C_{6}H_{3}(6-^{t}BuC_{6}H_{3}O)_{2}]^{3−},$ THF = tetrahydrofuran ) to triphenylphosphine $(PPh_{3})$ in THF produces $[^{t}BuOCO]Cr^{III}(THF)_{3}$ (1) and triphenylphosphine oxide $(OPPh_{3})$ at a rate of 69.5(±1.9) $M^{−1}s^{−1}$ (22 °C). Identical rate constants were attained when acetonitrile (MeCN) and dichloromethane /THF $(CH_{2}Cl_{2}/THF)$ were used as solvents . Electron paramagnetic resonance ( EPR ) data shows that the six-coordinate complex, $[^{t}BuOCO]Cr^{V}(O)(THF)_{2}$ (2a) forms upon addition of THF to 2, suggesting 2a as the active OAT species in THF. Similarly, addition of $OPPh_{3}$ has no influence on the rate of OAT, but the addition of triphenylphosphorus ylide $(CH_{2}PPh_{3})$ to form $[^{t}BuOCO]Cr^{V}(O)(CH_{2}PPh_{3})$ (4) prevents OAT to $PPh_{3}.$ In $CH_{2}Cl_{2},$ a $[Cr^{IV}]_{2}(μ-O)$ intermediate forms during the OAT from 2 to $PPh_{3}.$ The OAT from $\{[^{t}BuOCO]Cr^{IV}(THF)\}_{2}(μ-O)$ (3) to $PPh_{3}$ reveals a zero-order dependence in $PPh_{3}$ indicating the dimer must first dissociate prior to OAT. The decay of 3versus time does not follow first-order kinetics due to the formation of a $[^{t}BuOCO]Cr^{III}(THF)$ species (5) that inhibits the dissociation of 3. The change in concentration of 3versus time during OAT was simulated to obtain approximate rate constants.
ISSN	14779226
Issue Number	8
Journal	Dalton Trans.
Volume Number	41
e-ISSN	13645447
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2012-02-28
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Chemistry
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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