Electronic Profiling of N-Phosphine Oxide-Substituted Imidazolin-2-ylidenes (PoxIms) and Imidazolidin-2-ylidenes (SPoxIms)

Jia Nuo Leung; Yutaka Mondori; Sensuke Ogoshi; Yoichi Hoshimoto; Han Vinh Huynh

doi:10.1021/acs.inorgchem.3c04600

Electronic Profiling of N-Phosphine Oxide-Substituted Imidazolin-2-ylidenes (PoxIms) and Imidazolidin-2-ylidenes (SPoxIms)

Inorg Chem. 2024 Mar 4;63(9):4344-4354. doi: 10.1021/acs.inorgchem.3c04600. Epub 2024 Feb 22.

Authors

Jia Nuo Leung¹, Yutaka Mondori², Sensuke Ogoshi², Yoichi Hoshimoto^{2

3}, Han Vinh Huynh¹

Affiliations

¹ Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, Singapore 117453, Republic of Singapore.
² Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.
³ Center for Future Innovation (CFi), Division of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.

PMID: 38387056
DOI: 10.1021/acs.inorgchem.3c04600

Abstract

A detailed electronic study of the N-phosphine oxide functionalized imidazolin-2-ylidenes (PoxIms) and imidazolidin-2-ylidenes (SPoxIms) has been performed experimentally using IR, ¹³C, and ⁷⁷Se NMR spectroscopies. While the net donor/acceptor properties of the (S)PoxIms could not be differentiated via IR spectroscopy (TEP), NMR spectroscopic methods (HEP, Se) reveal that the (S)PoxIms are slightly weaker σ-donors but stronger π-acceptors compared to common NHCs. Moreover, backbone and substituent-effects could also be resolved by the latter, allowing for a ranking of their electronic properties. Finally, the donicities of these well-designed NHC ligands in their bidentate κ²-C,O modes were evaluated using HEP2 and compared to those of classical chelators.