Metal-Ligand Cooperative Reactivity in the (pseudo)-Dearomatized PNX(P) Systems: the Influence of the Zwitterionic Form in Dearomatized Pincer Complexes
Type
ArticleAuthors
Goncalves, TheoHuang, Kuo-Wei

KAUST Department
Chemical Science ProgramHomogeneous Catalysis Laboratory (HCL)
KAUST Catalysis Center (KCC)
Physical Science and Engineering (PSE) Division
Date
2017-09-14Online Publication Date
2017-09-14Print Publication Date
2017-09-27Permanent link to this record
http://hdl.handle.net/10754/625752
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Show full item recordAbstract
The concept of aromaticity in pincer ligands and complexes was discussed in order to provide insights into their metal-ligand cooperative activities. The aromatic PNx(P) and dearomatized PNx(P)* pincer ligands and the corresponding transition metal complexes were studied with the nucleus-independent chemical shift (NICSzz), anisotropy of the current (induced) density (ACID), isochemical shielding surfaces (ICSSzz), harmonic oscillator model of aromaticity (HOMA), MCBO, Shannon aromaticity, and natural bond order (NBO) analyses. The study on the model systems showed that for the dearomatized species the decrease of the NICS(1)zz value comes with the larger contribution of the aromatic zwitterionic mesomeric form. In all examples, the incorporation of the metal center into the pincer ligand decreases the NICS(1)zz values. The DFT calculations support the dearomatized pyridine ring in PNP* or PNN* ligand indeed being nonaromatic, in contrast to the PN3(P)* ligand which has partial aromatic character due to the larger contribution of the zwitterionic resonance structure. The difference in aromaticity between the rings contributes to the thermodynamic balance of the metal ligand cooperative reactions, changing the energetics of the process when different dearomatized pincer ligands are used. This was further exemplified by aromaticity analysis of the heterolytic hydrogen cleavage reaction of ruthenium PNN complexes of Milstein and the PN3 of Huang, with similar geometries but distinctive thermodynamic preference.Citation
Gonçalves TP, Huang K-W (2017) Metal–Ligand Cooperative Reactivity in the (Pseudo)-Dearomatized PNx(P) Systems: The Influence of the Zwitterionic Form in Dearomatized Pincer Complexes. Journal of the American Chemical Society 139: 13442–13449. Available: http://dx.doi.org/10.1021/jacs.7b06305.Sponsors
We acknowledge the service of NOOR 2, Shaheen 2 High Performance Computing Facilities, and financial support from King Abdullah University of Science and Technology (KAUST).Publisher
American Chemical Society (ACS)PubMed ID
28862844Additional Links
http://pubs.acs.org/doi/abs/10.1021/jacs.7b06305http://pubs.acs.org/doi/abs/10.1021/jacs.7b06305
ae974a485f413a2113503eed53cd6c53
10.1021/jacs.7b06305
Scopus Count
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