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Issue 8, 2012
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The influence of reversible trianionic pincer OCO3−μ-oxo Criv dimer formation ([Criv]2(μ-O)) and donor ligands in oxygen-atom-transfer (OAT)

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Abstract

The oxygen-atom-transfer (OAT) from [tBuOCO]CrV(O)(THF) (2) (where tBuOCO = [2,6-C6H3(6-tBuC6H3O)2]3, THF = tetrahydrofuran) to triphenylphosphine (PPh3) in THF produces [tBuOCO]CrIII(THF)3 (1) and triphenylphosphine oxide (OPPh3) at a rate of 69.5(±1.9) M−1s−1 (22 °C). Identical rate constants were attained when acetonitrile (MeCN) and dichloromethane/THF (CH2Cl2/THF) were used as solvents. Electron paramagnetic resonance (EPR) data shows that the six-coordinate complex, [tBuOCO]CrV(O)(THF)2 (2a) forms upon addition of THF to 2, suggesting 2a as the active OAT species in THF. Similarly, addition of OPPh3 has no influence on the rate of OAT, but the addition of triphenylphosphorus ylide (CH2PPh3) to form [tBuOCO]CrV(O)(CH2PPh3) (4) prevents OAT to PPh3. In CH2Cl2, a [CrIV]2(μ-O) intermediate forms during the OAT from 2 to PPh3. The OAT from {[tBuOCO]CrIV(THF)}2(μ-O) (3) to PPh3 reveals a zero-order dependence in PPh3 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 [tBuOCO]CrIII(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.

Graphical abstract: The influence of reversible trianionic pincer OCO3−μ-oxo Criv dimer formation ([Criv]2(μ-O)) and donor ligands in oxygen-atom-transfer (OAT)

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Article information


Submitted
13 Jun 2011
Accepted
26 Sep 2011
First published
18 Nov 2011

Dalton Trans., 2012,41, 2237-2246
Article type
Paper

The influence of reversible trianionic pincer OCO3−μ-oxo CrIV dimer formation ([CrIV]2(μ-O)) and donor ligands in oxygen-atom-transfer (OAT)

M. E. O'Reilly, T. J. Del Castillo, K. A. Abboud and A. S. Veige, Dalton Trans., 2012, 41, 2237
DOI: 10.1039/C1DT11104C

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