Metal-Ligand Cooperative Reactivity in the (pseudo)-Dearomatized PNX(P) Systems: the Influence of the Zwitterionic Form in Dearomatized Pincer Complexes
MetadataShow full item record
AbstractThe 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.
CitationGonçalves 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.
SponsorsWe acknowledge the service of NOOR 2, Shaheen 2 High Performance Computing Facilities, and financial support from King Abdullah University of Science and Technology (KAUST).
PublisherAmerican Chemical Society (ACS)
- Intramolecular C-H/O-H bond cleavage with water and alcohol using a phosphine-free ruthenium carbene NCN pincer complex.
- Authors: Prokopchuk DE, Tsui BT, Lough AJ, Morris RH
- Issue date: 2014 Dec 15
- Modularly designed transition metal PNP and PCP pincer complexes based on aminophosphines: synthesis and catalytic applications.
- Authors: Benito-Garagorri D, Kirchner K
- Issue date: 2008 Feb
- Synthesis, structures, and dearomatization by deprotonation of iron complexes featuring bipyridine-based PNN pincer ligands.
- Authors: Zell T, Langer R, Iron MA, Konstantinovski L, Shimon LJ, Diskin-Posner Y, Leitus G, Balaraman E, Ben-David Y, Milstein D
- Issue date: 2013 Aug 19
- Hydrogenation and dehydrogenation iron pincer catalysts capable of metal-ligand cooperation by aromatization/dearomatization.
- Authors: Zell T, Milstein D
- Issue date: 2015 Jul 21
- Ru(0) and Ru(II) nitrosyl pincer complexes: structure, reactivity, and catalytic activity.
- Authors: Fogler E, Iron MA, Zhang J, Ben-David Y, Diskin-Posner Y, Leitus G, Shimon LJ, Milstein D
- Issue date: 2013 Oct 7