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)

Matthew E. O'Reilly; Trevor J. Del Castillo; Khalil A. Abboud; Adam S. Veige

doi:10.1039/c1dt11104c

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)

Matthew E. O'Reilly, Trevor J. Del Castillo, Khalil A. Abboud, Adam S. Veige

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Abstract

The oxygen-atom-transfer (OAT) from [ ^tBuOCO]Cr ^v(O)(THF) (2) (where ^tBuOCO = [2,6-C ₆H ₃(6- ^tBuC ₆H ₃O) ₂] ^3-, THF = tetrahydrofuran) to triphenylphosphine (PPh ₃) in THF produces [ ^tBuOCO]Cr ⁱⁱⁱ(THF) ₃ (1) and triphenylphosphine oxide (OPPh ₃) at a rate of 69.5(±1.9) M ^-1s ^-1 (22 °C). Identical rate constants were attained when acetonitrile (MeCN) and dichloromethane/THF (CH ₂Cl ₂/THF) were used as solvents. Electron paramagnetic resonance (EPR) data shows that the six-coordinate complex, [ ^tBuOCO]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 ₂PPh ₃) to form [ ^tBuOCO]Cr ^v(O)(CH ₂PPh ₃) (4) prevents OAT to PPh ₃. In CH ₂Cl ₂, a [Cr ^iv] ₂(μ-O) intermediate forms during the OAT from 2 to PPh ₃. The OAT from {[ ^tBuOCO]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 [ ^tBuOCO]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.

Original language	English (US)
Pages (from-to)	2237-2246
Number of pages	10
Journal	Dalton Transactions
Volume	41
Issue number	8
DOIs	https://doi.org/10.1039/c1dt11104c
State	Published - Feb 28 2012
Externally published	Yes

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Inorganic Chemistry

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10.1039/c1dt11104c

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@article{a8e073249b03405eb8b407ef2a17dff9,

title = "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)",

abstract = "The oxygen-atom-transfer (OAT) from [ tBuOCO]Cr v(O)(THF) (2) (where tBuOCO = [2,6-C 6H 3(6- tBuC 6H 3O) 2] 3-, THF = tetrahydrofuran) to triphenylphosphine (PPh 3) in THF produces [ tBuOCO]Cr iii(THF) 3 (1) and triphenylphosphine oxide (OPPh 3) at a rate of 69.5(±1.9) M -1s -1 (22 °C). Identical rate constants were attained when acetonitrile (MeCN) and dichloromethane/THF (CH 2Cl 2/THF) were used as solvents. Electron paramagnetic resonance (EPR) data shows that the six-coordinate complex, [ tBuOCO]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 2PPh 3) to form [ tBuOCO]Cr v(O)(CH 2PPh 3) (4) prevents OAT to PPh 3. In CH 2Cl 2, a [Cr iv] 2(μ-O) intermediate forms during the OAT from 2 to PPh 3. The OAT from {[ tBuOCO]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 [ tBuOCO]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.",

author = "O'Reilly, {Matthew E.} and {Del Castillo}, {Trevor J.} and Abboud, {Khalil A.} and Veige, {Adam S.}",

year = "2012",

month = feb,

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doi = "10.1039/c1dt11104c",

language = "English (US)",

volume = "41",

pages = "2237--2246",

journal = "Dalton Transactions",

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publisher = "Royal Society of Chemistry",

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T1 - 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)

AU - O'Reilly, Matthew E.

AU - Del Castillo, Trevor J.

AU - Abboud, Khalil A.

AU - Veige, Adam S.

PY - 2012/2/28

Y1 - 2012/2/28

N2 - The oxygen-atom-transfer (OAT) from [ tBuOCO]Cr v(O)(THF) (2) (where tBuOCO = [2,6-C 6H 3(6- tBuC 6H 3O) 2] 3-, THF = tetrahydrofuran) to triphenylphosphine (PPh 3) in THF produces [ tBuOCO]Cr iii(THF) 3 (1) and triphenylphosphine oxide (OPPh 3) at a rate of 69.5(±1.9) M -1s -1 (22 °C). Identical rate constants were attained when acetonitrile (MeCN) and dichloromethane/THF (CH 2Cl 2/THF) were used as solvents. Electron paramagnetic resonance (EPR) data shows that the six-coordinate complex, [ tBuOCO]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 2PPh 3) to form [ tBuOCO]Cr v(O)(CH 2PPh 3) (4) prevents OAT to PPh 3. In CH 2Cl 2, a [Cr iv] 2(μ-O) intermediate forms during the OAT from 2 to PPh 3. The OAT from {[ tBuOCO]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 [ tBuOCO]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.

AB - The oxygen-atom-transfer (OAT) from [ tBuOCO]Cr v(O)(THF) (2) (where tBuOCO = [2,6-C 6H 3(6- tBuC 6H 3O) 2] 3-, THF = tetrahydrofuran) to triphenylphosphine (PPh 3) in THF produces [ tBuOCO]Cr iii(THF) 3 (1) and triphenylphosphine oxide (OPPh 3) at a rate of 69.5(±1.9) M -1s -1 (22 °C). Identical rate constants were attained when acetonitrile (MeCN) and dichloromethane/THF (CH 2Cl 2/THF) were used as solvents. Electron paramagnetic resonance (EPR) data shows that the six-coordinate complex, [ tBuOCO]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 2PPh 3) to form [ tBuOCO]Cr v(O)(CH 2PPh 3) (4) prevents OAT to PPh 3. In CH 2Cl 2, a [Cr iv] 2(μ-O) intermediate forms during the OAT from 2 to PPh 3. The OAT from {[ tBuOCO]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 [ tBuOCO]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.

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JO - Dalton Transactions

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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)

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