Ligand-directed Reactivity in Dioxygen and Water Binding to cis-[Pd(NHC)2(η2-O2)]

Taryn D. Palluccio, Xiaochen Cai, Subhojit Majumdar, Leonardo F. Serafim, Neil C. Tomson, Karl Wieghardt, Catherine S.J. Cazin, Steven P. Nolan, Elena V. Rybak-Akimova, Miguel Angel Fernández-González, Manuel Temprado, Burjor Captain, Carl Hoff

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Reaction of [Pd(IPr)2] (IPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) and O2 leads to the surprising discovery that at low temperature the initial reaction product is a highly labile peroxide complex cis-[Pd(IPr)2(η2-O2)]. At temperatures of above ≈-40°C, cis-[Pd(IPr)2(η2-O2)] adds a second O2 to form trans-[Pd(IPr)2(η1-O2)2]. Squid magnetometry and EPR studies yield data that are consistent with a singlet diradical ground state with a thermally accessible triplet state for this unique bis-superoxide complex. In addition to reaction with O2, cis-[Pd(IPr)2(η2-O2)] reacts at low temperature with H2O in methanol/ether solution to form trans-[Pd(IPr)2(OH)(OOH)]. The crystal structure of trans-[Pd(IPr)2(OOH)(OH)] is reported. Neither reaction with O2 nor reaction with H2O occur under comparable conditions for cis-[Pd(IMes)2(η2-O2)] (IMes = 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene). The increased reactivity of cis-[Pd(IPr)2(η2-O2)] is attributed to the enthalpy of binding of O2 to [Pd(IPr)2] (-14.5 ± 1.0 kcal/mol) that is approximately half that of [Pd(IMes)2] (-27.9 ± 1.5 kcal/mol). Computational studies identify the cause as interligand repulsion forcing a wider C-Pd-C angle and tilting of the NHC plane in cis-[Pd(IPr)2(η2-O2)]. Arene-arene interactions are more favorable and serve to further stabilize cis-[Pd(IMes)2(η2-O2)]. Inclusion of dispersion effects in DFT calculations leads to improved agreement between experimental and computational enthalpies of O2 binding. A complete reaction diagram is constructed for formation of trans-[Pd(IPr)2(η1-O2)2] and leads to the conclusion that kinetic factors inhibit formation of trans-[Pd(IMes)2(η1-O2)2] at the low temperatures at which it is thermodynamically favored. Failure to detect the predicted T-shaped intermediate trans-[Pd(NHC)2(η1-O2)] for either NHC = IMes or IPr is attributed to dynamic effects. A partial potential energy diagram for initial binding of O2 is constructed. A range of low energy pathways at different angles of approach are present and blur the distinction between pure »side-on» or »end-on» trajectories for oxygen binding.

Original languageEnglish (US)
JournalUnknown Journal
DOIs
StateAccepted/In press - Sep 16 2017

Fingerprint

reactivity
Ligands
Oxygen
ligands
Temperature
Water
water
Enthalpy
Magnetometry
imidazoles
Decapodiformes
enthalpy
diagrams
Peroxides
Potential energy
Reaction products
Discrete Fourier transforms
Superoxides
Ether
Ground state

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Palluccio, T. D., Cai, X., Majumdar, S., Serafim, L. F., Tomson, N. C., Wieghardt, K., ... Hoff, C. (Accepted/In press). Ligand-directed Reactivity in Dioxygen and Water Binding to cis-[Pd(NHC)2(η2-O2)]. Unknown Journal. https://doi.org/10.1021/jacs.7b09905

Ligand-directed Reactivity in Dioxygen and Water Binding to cis-[Pd(NHC)2(η2-O2)]. / Palluccio, Taryn D.; Cai, Xiaochen; Majumdar, Subhojit; Serafim, Leonardo F.; Tomson, Neil C.; Wieghardt, Karl; Cazin, Catherine S.J.; Nolan, Steven P.; Rybak-Akimova, Elena V.; Fernández-González, Miguel Angel; Temprado, Manuel; Captain, Burjor; Hoff, Carl.

In: Unknown Journal, 16.09.2017.

Research output: Contribution to journalArticle

Palluccio, TD, Cai, X, Majumdar, S, Serafim, LF, Tomson, NC, Wieghardt, K, Cazin, CSJ, Nolan, SP, Rybak-Akimova, EV, Fernández-González, MA, Temprado, M, Captain, B & Hoff, C 2017, 'Ligand-directed Reactivity in Dioxygen and Water Binding to cis-[Pd(NHC)2(η2-O2)]', Unknown Journal. https://doi.org/10.1021/jacs.7b09905
Palluccio TD, Cai X, Majumdar S, Serafim LF, Tomson NC, Wieghardt K et al. Ligand-directed Reactivity in Dioxygen and Water Binding to cis-[Pd(NHC)2(η2-O2)]. Unknown Journal. 2017 Sep 16. https://doi.org/10.1021/jacs.7b09905
Palluccio, Taryn D. ; Cai, Xiaochen ; Majumdar, Subhojit ; Serafim, Leonardo F. ; Tomson, Neil C. ; Wieghardt, Karl ; Cazin, Catherine S.J. ; Nolan, Steven P. ; Rybak-Akimova, Elena V. ; Fernández-González, Miguel Angel ; Temprado, Manuel ; Captain, Burjor ; Hoff, Carl. / Ligand-directed Reactivity in Dioxygen and Water Binding to cis-[Pd(NHC)2(η2-O2)]. In: Unknown Journal. 2017.
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title = "Ligand-directed Reactivity in Dioxygen and Water Binding to cis-[Pd(NHC)2(η2-O2)]",
abstract = "Reaction of [Pd(IPr)2] (IPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) and O2 leads to the surprising discovery that at low temperature the initial reaction product is a highly labile peroxide complex cis-[Pd(IPr)2(η2-O2)]. At temperatures of above ≈-40°C, cis-[Pd(IPr)2(η2-O2)] adds a second O2 to form trans-[Pd(IPr)2(η1-O2)2]. Squid magnetometry and EPR studies yield data that are consistent with a singlet diradical ground state with a thermally accessible triplet state for this unique bis-superoxide complex. In addition to reaction with O2, cis-[Pd(IPr)2(η2-O2)] reacts at low temperature with H2O in methanol/ether solution to form trans-[Pd(IPr)2(OH)(OOH)]. The crystal structure of trans-[Pd(IPr)2(OOH)(OH)] is reported. Neither reaction with O2 nor reaction with H2O occur under comparable conditions for cis-[Pd(IMes)2(η2-O2)] (IMes = 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene). The increased reactivity of cis-[Pd(IPr)2(η2-O2)] is attributed to the enthalpy of binding of O2 to [Pd(IPr)2] (-14.5 ± 1.0 kcal/mol) that is approximately half that of [Pd(IMes)2] (-27.9 ± 1.5 kcal/mol). Computational studies identify the cause as interligand repulsion forcing a wider C-Pd-C angle and tilting of the NHC plane in cis-[Pd(IPr)2(η2-O2)]. Arene-arene interactions are more favorable and serve to further stabilize cis-[Pd(IMes)2(η2-O2)]. Inclusion of dispersion effects in DFT calculations leads to improved agreement between experimental and computational enthalpies of O2 binding. A complete reaction diagram is constructed for formation of trans-[Pd(IPr)2(η1-O2)2] and leads to the conclusion that kinetic factors inhibit formation of trans-[Pd(IMes)2(η1-O2)2] at the low temperatures at which it is thermodynamically favored. Failure to detect the predicted T-shaped intermediate trans-[Pd(NHC)2(η1-O2)] for either NHC = IMes or IPr is attributed to dynamic effects. A partial potential energy diagram for initial binding of O2 is constructed. A range of low energy pathways at different angles of approach are present and blur the distinction between pure »side-on» or »end-on» trajectories for oxygen binding.",
author = "Palluccio, {Taryn D.} and Xiaochen Cai and Subhojit Majumdar and Serafim, {Leonardo F.} and Tomson, {Neil C.} and Karl Wieghardt and Cazin, {Catherine S.J.} and Nolan, {Steven P.} and Rybak-Akimova, {Elena V.} and Fern{\'a}ndez-Gonz{\'a}lez, {Miguel Angel} and Manuel Temprado and Burjor Captain and Carl Hoff",
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TY - JOUR

T1 - Ligand-directed Reactivity in Dioxygen and Water Binding to cis-[Pd(NHC)2(η2-O2)]

AU - Palluccio, Taryn D.

AU - Cai, Xiaochen

AU - Majumdar, Subhojit

AU - Serafim, Leonardo F.

AU - Tomson, Neil C.

AU - Wieghardt, Karl

AU - Cazin, Catherine S.J.

AU - Nolan, Steven P.

AU - Rybak-Akimova, Elena V.

AU - Fernández-González, Miguel Angel

AU - Temprado, Manuel

AU - Captain, Burjor

AU - Hoff, Carl

PY - 2017/9/16

Y1 - 2017/9/16

N2 - Reaction of [Pd(IPr)2] (IPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) and O2 leads to the surprising discovery that at low temperature the initial reaction product is a highly labile peroxide complex cis-[Pd(IPr)2(η2-O2)]. At temperatures of above ≈-40°C, cis-[Pd(IPr)2(η2-O2)] adds a second O2 to form trans-[Pd(IPr)2(η1-O2)2]. Squid magnetometry and EPR studies yield data that are consistent with a singlet diradical ground state with a thermally accessible triplet state for this unique bis-superoxide complex. In addition to reaction with O2, cis-[Pd(IPr)2(η2-O2)] reacts at low temperature with H2O in methanol/ether solution to form trans-[Pd(IPr)2(OH)(OOH)]. The crystal structure of trans-[Pd(IPr)2(OOH)(OH)] is reported. Neither reaction with O2 nor reaction with H2O occur under comparable conditions for cis-[Pd(IMes)2(η2-O2)] (IMes = 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene). The increased reactivity of cis-[Pd(IPr)2(η2-O2)] is attributed to the enthalpy of binding of O2 to [Pd(IPr)2] (-14.5 ± 1.0 kcal/mol) that is approximately half that of [Pd(IMes)2] (-27.9 ± 1.5 kcal/mol). Computational studies identify the cause as interligand repulsion forcing a wider C-Pd-C angle and tilting of the NHC plane in cis-[Pd(IPr)2(η2-O2)]. Arene-arene interactions are more favorable and serve to further stabilize cis-[Pd(IMes)2(η2-O2)]. Inclusion of dispersion effects in DFT calculations leads to improved agreement between experimental and computational enthalpies of O2 binding. A complete reaction diagram is constructed for formation of trans-[Pd(IPr)2(η1-O2)2] and leads to the conclusion that kinetic factors inhibit formation of trans-[Pd(IMes)2(η1-O2)2] at the low temperatures at which it is thermodynamically favored. Failure to detect the predicted T-shaped intermediate trans-[Pd(NHC)2(η1-O2)] for either NHC = IMes or IPr is attributed to dynamic effects. A partial potential energy diagram for initial binding of O2 is constructed. A range of low energy pathways at different angles of approach are present and blur the distinction between pure »side-on» or »end-on» trajectories for oxygen binding.

AB - Reaction of [Pd(IPr)2] (IPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) and O2 leads to the surprising discovery that at low temperature the initial reaction product is a highly labile peroxide complex cis-[Pd(IPr)2(η2-O2)]. At temperatures of above ≈-40°C, cis-[Pd(IPr)2(η2-O2)] adds a second O2 to form trans-[Pd(IPr)2(η1-O2)2]. Squid magnetometry and EPR studies yield data that are consistent with a singlet diradical ground state with a thermally accessible triplet state for this unique bis-superoxide complex. In addition to reaction with O2, cis-[Pd(IPr)2(η2-O2)] reacts at low temperature with H2O in methanol/ether solution to form trans-[Pd(IPr)2(OH)(OOH)]. The crystal structure of trans-[Pd(IPr)2(OOH)(OH)] is reported. Neither reaction with O2 nor reaction with H2O occur under comparable conditions for cis-[Pd(IMes)2(η2-O2)] (IMes = 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene). The increased reactivity of cis-[Pd(IPr)2(η2-O2)] is attributed to the enthalpy of binding of O2 to [Pd(IPr)2] (-14.5 ± 1.0 kcal/mol) that is approximately half that of [Pd(IMes)2] (-27.9 ± 1.5 kcal/mol). Computational studies identify the cause as interligand repulsion forcing a wider C-Pd-C angle and tilting of the NHC plane in cis-[Pd(IPr)2(η2-O2)]. Arene-arene interactions are more favorable and serve to further stabilize cis-[Pd(IMes)2(η2-O2)]. Inclusion of dispersion effects in DFT calculations leads to improved agreement between experimental and computational enthalpies of O2 binding. A complete reaction diagram is constructed for formation of trans-[Pd(IPr)2(η1-O2)2] and leads to the conclusion that kinetic factors inhibit formation of trans-[Pd(IMes)2(η1-O2)2] at the low temperatures at which it is thermodynamically favored. Failure to detect the predicted T-shaped intermediate trans-[Pd(NHC)2(η1-O2)] for either NHC = IMes or IPr is attributed to dynamic effects. A partial potential energy diagram for initial binding of O2 is constructed. A range of low energy pathways at different angles of approach are present and blur the distinction between pure »side-on» or »end-on» trajectories for oxygen binding.

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