Interconversion of Molybdenum Imido and Amido Complexes by Proton-Coupled Electron Transfer

Máté J. Bezdek; Paul J. Chirik

doi:10.1002/anie.201708406

Interconversion of Molybdenum Imido and Amido Complexes by Proton-Coupled Electron Transfer

Máté J. Bezdek, Paul J. Chirik

Chemistry

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

42 Scopus citations

Abstract

Interconversion of the molybdenum amido [(^PhTpy)(PPh₂Me)₂Mo(NHtBuAr)][BArF²⁴] (^PhTpy=4′-Ph-2,2′,6′,2“-terpyridine; tBuAr=4-tert-butyl-C₆H₄; ArF²⁴=(C₆H₃-3,5-(CF₃)₂)₄) and imido [(^PhTpy)(PPh₂Me)₂Mo(NtBuAr)][BArF²⁴] complexes has been accomplished by proton-coupled electron transfer. The 2,4,6-tri-tert-butylphenoxyl radical was used as an oxidant and the non-classical ammine complex [(^PhTpy)(PPh₂Me)₂Mo(NH₃)][BArF²⁴] as the reductant. The N−H bond dissociation free energy (BDFE) of the amido N−H bond formed and cleaved in the sequence was experimentally bracketed between 45.8 and 52.3 kcal mol⁻¹, in agreement with a DFT-computed value of 48 kcal mol⁻¹. The N−H BDFE in combination with electrochemical data eliminate proton transfer as the first step in the N−H bond-forming sequence and favor initial electron transfer or concerted pathways.

Original language	English (US)
Pages (from-to)	2224-2228
Number of pages	5
Journal	Angewandte Chemie - International Edition
Volume	57
Issue number	8
DOIs	https://doi.org/10.1002/anie.201708406
State	Published - Feb 19 2018

All Science Journal Classification (ASJC) codes

General Chemistry
Catalysis

Keywords

amido ligands
ammonia chemistry
imido ligands
molybdenum complexes
thermochemistry

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title = "Interconversion of Molybdenum Imido and Amido Complexes by Proton-Coupled Electron Transfer",

abstract = "Interconversion of the molybdenum amido [(PhTpy)(PPh2Me)2Mo(NHtBuAr)][BArF24] (PhTpy=4′-Ph-2,2′,6′,2“-terpyridine; tBuAr=4-tert-butyl-C6H4; ArF24=(C6H3-3,5-(CF3)2)4) and imido [(PhTpy)(PPh2Me)2Mo(NtBuAr)][BArF24] complexes has been accomplished by proton-coupled electron transfer. The 2,4,6-tri-tert-butylphenoxyl radical was used as an oxidant and the non-classical ammine complex [(PhTpy)(PPh2Me)2Mo(NH3)][BArF24] as the reductant. The N−H bond dissociation free energy (BDFE) of the amido N−H bond formed and cleaved in the sequence was experimentally bracketed between 45.8 and 52.3 kcal mol−1, in agreement with a DFT-computed value of 48 kcal mol−1. The N−H BDFE in combination with electrochemical data eliminate proton transfer as the first step in the N−H bond-forming sequence and favor initial electron transfer or concerted pathways.",

keywords = "amido ligands, ammonia chemistry, imido ligands, molybdenum complexes, thermochemistry",

author = "Bezdek, {M{\'a}t{\'e} J.} and Chirik, {Paul J.}",

note = "Publisher Copyright: {\textcopyright} 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim",

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AU - Bezdek, Máté J.

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N2 - Interconversion of the molybdenum amido [(PhTpy)(PPh2Me)2Mo(NHtBuAr)][BArF24] (PhTpy=4′-Ph-2,2′,6′,2“-terpyridine; tBuAr=4-tert-butyl-C6H4; ArF24=(C6H3-3,5-(CF3)2)4) and imido [(PhTpy)(PPh2Me)2Mo(NtBuAr)][BArF24] complexes has been accomplished by proton-coupled electron transfer. The 2,4,6-tri-tert-butylphenoxyl radical was used as an oxidant and the non-classical ammine complex [(PhTpy)(PPh2Me)2Mo(NH3)][BArF24] as the reductant. The N−H bond dissociation free energy (BDFE) of the amido N−H bond formed and cleaved in the sequence was experimentally bracketed between 45.8 and 52.3 kcal mol−1, in agreement with a DFT-computed value of 48 kcal mol−1. The N−H BDFE in combination with electrochemical data eliminate proton transfer as the first step in the N−H bond-forming sequence and favor initial electron transfer or concerted pathways.

AB - Interconversion of the molybdenum amido [(PhTpy)(PPh2Me)2Mo(NHtBuAr)][BArF24] (PhTpy=4′-Ph-2,2′,6′,2“-terpyridine; tBuAr=4-tert-butyl-C6H4; ArF24=(C6H3-3,5-(CF3)2)4) and imido [(PhTpy)(PPh2Me)2Mo(NtBuAr)][BArF24] complexes has been accomplished by proton-coupled electron transfer. The 2,4,6-tri-tert-butylphenoxyl radical was used as an oxidant and the non-classical ammine complex [(PhTpy)(PPh2Me)2Mo(NH3)][BArF24] as the reductant. The N−H bond dissociation free energy (BDFE) of the amido N−H bond formed and cleaved in the sequence was experimentally bracketed between 45.8 and 52.3 kcal mol−1, in agreement with a DFT-computed value of 48 kcal mol−1. The N−H BDFE in combination with electrochemical data eliminate proton transfer as the first step in the N−H bond-forming sequence and favor initial electron transfer or concerted pathways.

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KW - imido ligands

KW - molybdenum complexes

KW - thermochemistry

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Interconversion of Molybdenum Imido and Amido Complexes by Proton-Coupled Electron Transfer

Abstract

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