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Interconversion of Molybdenum Imido and Amido Complexes by Proton‐Coupled Electron Transfer
Author(s) -
Bezdek Máté J.,
Chirik Paul J.
Publication year - 2018
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201708406
Subject(s) - chemistry , molybdenum , proton , electron transfer , bond dissociation energy , dissociation (chemistry) , proton coupled electron transfer , crystallography , electrochemistry , bond length , medicinal chemistry , stereochemistry , photochemistry , inorganic chemistry , crystal structure , electrode , physics , quantum mechanics
Abstract Interconversion of the molybdenum amido [( Ph Tpy)(PPh 2 Me) 2 Mo(NH t BuAr)][BArF 24 ] ( Ph Tpy=4′‐Ph‐2,2′,6′,2“‐terpyridine; t BuAr=4‐ tert ‐butyl‐C 6 H 4 ; ArF 24 =(C 6 H 3 ‐3,5‐(CF 3 ) 2 ) 4 ) and imido [( Ph Tpy)(PPh 2 Me) 2 Mo(N t BuAr)][BArF 24 ] 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 [( Ph Tpy)(PPh 2 Me) 2 Mo(NH 3 )][BArF 24 ] 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.