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Halogen Photoelimination from Monomeric Nickel(III) Complexes Enabled by the Secondary Coordination Sphere

Hwang, Seung Jun and Anderson, Bryce L. and Powers, David C. and Maher, Andrew G. and Hadt, Ryan G. and Nocera, Daniel G. (2015) Halogen Photoelimination from Monomeric Nickel(III) Complexes Enabled by the Secondary Coordination Sphere. Organometallics, 34 (19). pp. 4766-4774. ISSN 0276-7333. doi:10.1021/acs.organomet.5b00568.

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Endothermic halogen elimination reactions, in which molecular halogen photoproducts are generated in the absence of chemical traps, are rare. Inspired by the proclivity of mononuclear Ni(III) complexes to participate in challenging bond-forming reactions in organometallic chemistry, we targeted Ni(III) trihalide complexes as platforms to explore halogen photoelimination. A suite of Ni(III) trihalide complexes supported by bidentate phosphine ligands has been synthesized and characterized. Multinuclear NMR, EPR, and electronic absorption spectroscopies, as well as single-crystal X-ray diffraction, have been utilized to characterize this suite of complexes as distorted square pyramidal, S = 1/2 mononuclear Ni(III) complexes. All complexes participate in clean halogen photoelimination in solution and in the solid state. Evolved halogen has been characterized by mass spectrometry and quantified chemically. Energy storage via halogen elimination was established by solution-phase calorimetry measurements; in all cases, halogen elimination is substantially endothermic. Time-resolved photochemical experiments have revealed a relatively long-lived photointermediate, which we assign to be a Ni(II) complex in which the photoextruded chlorine radical interacts with a ligand-based aryl group. Computational studies suggest that the observed intermediate arises from a dissociative LMCT excited state. The participation of secondary coordination sphere interactions to suppress back-reactions is an attractive design element in the development of energy-storing halogen photoelimination involving first-row transition metal complexes.

Item Type:Article
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URLURL TypeDescription Information
Hadt, Ryan G.0000-0001-6026-1358
Nocera, Daniel G.0000-0001-5055-320X
Additional Information:© 2015 American Chemical Society. Received: July 1, 2015; Published: September 4, 2015. Special Issue: Gregory Hillhouse Issue. We gratefully acknowledge the NSF for funding (CHE-1464232). D.C.P. is supported by a Ruth L. Kirchenstein National Research Service award (F32GM103211). Use of APS was supported by the U.S. DOE, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. We thank Prof. G. M. Whitesides for access to his laboratory’s calorimetry instrumentation. In memory of our friend and colleague, Greg. Author Contributions: S. J. Hwang and B. L. Anderson contributed equally to this work. The authors declare no competing financial interest.
Funding AgencyGrant Number
NIH Predoctoral FellowshipF32GM103211
Department of Energy (DOE)DE-AC02-06CH11357
Issue or Number:19
Record Number:CaltechAUTHORS:20180612-080212389
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Official Citation:Halogen Photoelimination from Monomeric Nickel(III) Complexes Enabled by the Secondary Coordination Sphere. Seung Jun Hwang, Bryce L. Anderson, David C. Powers, Andrew G. Maher, Ryan G. Hadt, and Daniel G. Nocera. Organometallics 2015 34 (19), 4766-4774. DOI: 10.1021/acs.organomet.5b00568
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86985
Deposited By: Tony Diaz
Deposited On:12 Jun 2018 16:29
Last Modified:15 Nov 2021 20:44

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