Premium
Bis(Iminophosphorano)‐Substituted Pyridinium Ions and their Corresponding Bispyridinylidene Organic Electron Donors
Author(s) -
Frenette Brandon L.,
Arsenault Nadine,
Walker Sarah L.,
Decken Andreas,
Dyker C. Adam
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202100318
Subject(s) - pyridinium , chemistry , saturated calomel electrode , electrochemistry , redox , aromaticity , ring (chemistry) , ion , deprotonation , chloride , medicinal chemistry , electron transfer , electron , inorganic chemistry , crystallography , electrode , photochemistry , organic chemistry , molecule , working electrode , physics , quantum mechanics
Optimized synthetic procedures for pyridinium ions featuring iminophosphorano (−N=PR 3 ; R=Ph, Cy) π‐donor substituents in the 2‐ and 4‐ positions are described. Crystallographic and theoretical studies reveal that the strongly donating substituents severely polarize the π‐electrons of the pyridyl ring at the expense of aromaticity. Moreover, the pyridinium ions are readily deprotonated to generate powerful bispyridinylidene (BPY) organic electron donors. Electrochemical studies show exceptionally low redox potentials for the two‐electron BPY/BPY 2+ couples, ranging from −1.71 V vs the saturated calomel electrode for 3PhPh (with four Ph 3 P=N− groups) to −1.85 V for 3CyCy (with four Cy 3 P=N− groups). These new compounds represent the most reducing neutral organic electron donors (OEDs) currently known. Some preliminary reductions involving 3CyCy showed enhanced capability owing to its low redox potential, such as the thermally activated reduction of an aryl chloride, but purification challenges were often encountered.