Synthesis and redox reactivity of a phosphine-ligated dichromium paddlewheel

Reed J. Eisenhart; Rebecca K. Carlson; Kelsey M. Boyle; Laura Gagliardi; Connie C. Lu

doi:10.1016/j.ica.2014.10.013

Synthesis and redox reactivity of a phosphine-ligated dichromium paddlewheel

Reed J. Eisenhart, Rebecca K. Carlson, Kelsey M. Boyle, Laura Gagliardi, Connie C. Lu

Research output: Contribution to journal › Article › peer-review

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Abstract

A pentadentate ligand platform, bis[2-(diisopropylphosphino-methylamino)phenyl]ether (1), abbreviated as H₂(PNONP), is introduced that enables the isolation of homodinuclear chromium complexes. In a one-step metalation using Cr(III) and Cr(II) chloride reagents, the bimetallic compounds, [Cr(μ-Cl)(PNONP)]₂ (2) and [Cr(PNONP)]₂ (3), respectively, were synthesized. These complexes have been characterized by X-ray diffraction, NMR spectroscopy, cyclic voltammetry, magnetometry, UV-Vis-NIR spectroscopy, combustion analysis, and computational methods. Complex 3 has a reasonably short Cr-Cr bond length of 2.1342(5) Å. Quantum chemical calculations support a diradical singlet ground-state with a formal triple bond between the chromium centers. By cyclic voltammetry, 3 exhibits two reversible oxidations at E = -470 and -750 mV versus FeCp₂^0/+. The one- and two-electron oxidized analogues, 3⁺ and 3²⁺, were generated in situ via chemical oxidation using ferrocenium. Based on in situ characterization of 3⁺ and 3²⁺, we hypothesize the oxidations are metal-based to yield Cr₂⁵⁺ and Cr₂⁶⁺ cores, respectively.

Original language	English (US)
Pages (from-to)	336-344
Number of pages	9
Journal	Inorganica Chimica Acta
Volume	424
DOIs	https://doi.org/10.1016/j.ica.2014.10.013
State	Published - Jan 1 2015

Bibliographical note

Funding Information:
The authors thank Dr. Eckhard Bill and Andreas Göbels (Max Planck Institute) for their expertise in SQUID data collection, as well as Dr. Victor G. Young, Jr. (UMN) for helpful discussions regarding X-ray crystallography. This research was primarily supported as part of the Inorganometallic Catalyst Design Center, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) , under Award DE-SC0012702 (computational studies), by the National Science Foundation (NSF) under Award CHE 1254621 (experimental work). C.C.L. is grateful to the Alfred P. Sloan Foundation for a research fellowship. R.K.C. thanks the NSF for a graduate fellowship. K.M.B. was funded by UROP . X-ray diffraction experiments were performed using a crystal diffractometer acquired through an NSF-MRI award (CHE-1229400) in the X-ray laboratory.

Publisher Copyright:
© 2014 Elsevier B.V. All rights reserved.

Keywords

Dichromium
Dinuclear
Homobimetallic
Metal-metal multiple bond
Phosphine

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10.1016/j.ica.2014.10.013

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title = "Synthesis and redox reactivity of a phosphine-ligated dichromium paddlewheel",

abstract = "A pentadentate ligand platform, bis[2-(diisopropylphosphino-methylamino)phenyl]ether (1), abbreviated as H2(PNONP), is introduced that enables the isolation of homodinuclear chromium complexes. In a one-step metalation using Cr(III) and Cr(II) chloride reagents, the bimetallic compounds, [Cr(μ-Cl)(PNONP)]2 (2) and [Cr(PNONP)]2 (3), respectively, were synthesized. These complexes have been characterized by X-ray diffraction, NMR spectroscopy, cyclic voltammetry, magnetometry, UV-Vis-NIR spectroscopy, combustion analysis, and computational methods. Complex 3 has a reasonably short Cr-Cr bond length of 2.1342(5) {\AA}. Quantum chemical calculations support a diradical singlet ground-state with a formal triple bond between the chromium centers. By cyclic voltammetry, 3 exhibits two reversible oxidations at E = -470 and -750 mV versus FeCp20/+. The one- and two-electron oxidized analogues, 3+ and 32+, were generated in situ via chemical oxidation using ferrocenium. Based on in situ characterization of 3+ and 32+, we hypothesize the oxidations are metal-based to yield Cr25+ and Cr26+ cores, respectively.",

keywords = "Dichromium, Dinuclear, Homobimetallic, Metal-metal multiple bond, Phosphine",

author = "Eisenhart, {Reed J.} and Carlson, {Rebecca K.} and Boyle, {Kelsey M.} and Laura Gagliardi and Lu, {Connie C.}",

note = "Funding Information: The authors thank Dr. Eckhard Bill and Andreas G{\"o}bels (Max Planck Institute) for their expertise in SQUID data collection, as well as Dr. Victor G. Young, Jr. (UMN) for helpful discussions regarding X-ray crystallography. This research was primarily supported as part of the Inorganometallic Catalyst Design Center, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) , under Award DE-SC0012702 (computational studies), by the National Science Foundation (NSF) under Award CHE 1254621 (experimental work). C.C.L. is grateful to the Alfred P. Sloan Foundation for a research fellowship. R.K.C. thanks the NSF for a graduate fellowship. K.M.B. was funded by UROP . X-ray diffraction experiments were performed using a crystal diffractometer acquired through an NSF-MRI award (CHE-1229400) in the X-ray laboratory. Publisher Copyright: {\textcopyright} 2014 Elsevier B.V. All rights reserved.",

year = "2015",

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doi = "10.1016/j.ica.2014.10.013",

language = "English (US)",

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TY - JOUR

T1 - Synthesis and redox reactivity of a phosphine-ligated dichromium paddlewheel

AU - Eisenhart, Reed J.

AU - Carlson, Rebecca K.

AU - Boyle, Kelsey M.

AU - Gagliardi, Laura

AU - Lu, Connie C.

N1 - Funding Information: The authors thank Dr. Eckhard Bill and Andreas Göbels (Max Planck Institute) for their expertise in SQUID data collection, as well as Dr. Victor G. Young, Jr. (UMN) for helpful discussions regarding X-ray crystallography. This research was primarily supported as part of the Inorganometallic Catalyst Design Center, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) , under Award DE-SC0012702 (computational studies), by the National Science Foundation (NSF) under Award CHE 1254621 (experimental work). C.C.L. is grateful to the Alfred P. Sloan Foundation for a research fellowship. R.K.C. thanks the NSF for a graduate fellowship. K.M.B. was funded by UROP . X-ray diffraction experiments were performed using a crystal diffractometer acquired through an NSF-MRI award (CHE-1229400) in the X-ray laboratory. Publisher Copyright: © 2014 Elsevier B.V. All rights reserved.

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Y1 - 2015/1/1

N2 - A pentadentate ligand platform, bis[2-(diisopropylphosphino-methylamino)phenyl]ether (1), abbreviated as H2(PNONP), is introduced that enables the isolation of homodinuclear chromium complexes. In a one-step metalation using Cr(III) and Cr(II) chloride reagents, the bimetallic compounds, [Cr(μ-Cl)(PNONP)]2 (2) and [Cr(PNONP)]2 (3), respectively, were synthesized. These complexes have been characterized by X-ray diffraction, NMR spectroscopy, cyclic voltammetry, magnetometry, UV-Vis-NIR spectroscopy, combustion analysis, and computational methods. Complex 3 has a reasonably short Cr-Cr bond length of 2.1342(5) Å. Quantum chemical calculations support a diradical singlet ground-state with a formal triple bond between the chromium centers. By cyclic voltammetry, 3 exhibits two reversible oxidations at E = -470 and -750 mV versus FeCp20/+. The one- and two-electron oxidized analogues, 3+ and 32+, were generated in situ via chemical oxidation using ferrocenium. Based on in situ characterization of 3+ and 32+, we hypothesize the oxidations are metal-based to yield Cr25+ and Cr26+ cores, respectively.

AB - A pentadentate ligand platform, bis[2-(diisopropylphosphino-methylamino)phenyl]ether (1), abbreviated as H2(PNONP), is introduced that enables the isolation of homodinuclear chromium complexes. In a one-step metalation using Cr(III) and Cr(II) chloride reagents, the bimetallic compounds, [Cr(μ-Cl)(PNONP)]2 (2) and [Cr(PNONP)]2 (3), respectively, were synthesized. These complexes have been characterized by X-ray diffraction, NMR spectroscopy, cyclic voltammetry, magnetometry, UV-Vis-NIR spectroscopy, combustion analysis, and computational methods. Complex 3 has a reasonably short Cr-Cr bond length of 2.1342(5) Å. Quantum chemical calculations support a diradical singlet ground-state with a formal triple bond between the chromium centers. By cyclic voltammetry, 3 exhibits two reversible oxidations at E = -470 and -750 mV versus FeCp20/+. The one- and two-electron oxidized analogues, 3+ and 32+, were generated in situ via chemical oxidation using ferrocenium. Based on in situ characterization of 3+ and 32+, we hypothesize the oxidations are metal-based to yield Cr25+ and Cr26+ cores, respectively.

KW - Dichromium

KW - Dinuclear

KW - Homobimetallic

KW - Metal-metal multiple bond

KW - Phosphine

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SN - 0020-1693

VL - 424

SP - 336

EP - 344

JO - Inorganica Chimica Acta

JF - Inorganica Chimica Acta

ER -

Synthesis and redox reactivity of a phosphine-ligated dichromium paddlewheel

Abstract

Bibliographical note

Keywords

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Energy Frontier Research Center For Inorganometallic Catalyst Design (DE-SC0012702)

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Synthesis and redox reactivity of a phosphine-ligated dichromium paddlewheel

Abstract

Bibliographical note

Keywords

Publisher link

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Projects

Energy Frontier Research Center For Inorganometallic Catalyst Design (DE-SC0012702)

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