@article {43605,
	title = {New Pyridine Dicarbene Pincer Ligands with Ring Expanded NHCs and their Nickel and Chromium Complexes},
	journal = {Chemistry - An Asian Journal},
	volume = {19},
	year = {2024},
	month = {2024},
	publisher = {John Wiley and Sons Ltd},
	abstract = {The pincer complexes [NiIIBr(CNC)]Br (4), [CrIIIBr3(CNC)] (5 a) and [CrIIIBr2.3Cl0.7(CNC)] (5 b), where CNC=3,3'-(pyridine-2,6-diyl)bis(1-mesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene), were obtained from the novel ligand CNC, generated in situ from the precursor (CHNCH)Br2 and [NiIIBr2(PPh3)2] or from [CrII{N(SiMe3)2}2(THF)2] and (CHNCH)Br2 by aminolysis, respectively. The tetrahedrally distorted square planar (τ4≅0.30) geometry and the singlet ground state of Ni in 4 were attributed to steric constraints of the CNC backbone. Computational methods highlighted the dependence of the coordination geometry and the singlet-triplet energy difference on the size of the N-substituent of the tetrahydropyrimidine wingtips and contrasted it to the situation in 5-membered imidazolin-2-ylidene pincer analogues. The octahedral CrIII metal center in 5 a and 5 b is presumably formed after one electron oxidation from CH2Cl2. 4/MAO and 5 a/MAO were catalysts of moderate activity for the oligomerization and polymerization of ethylene, respectively. The analogous (CH^N^CH)Br2 precursor, where (CH^N^CH)=3,3'-(pyridine-2,6-diylbis(methylene))bis(1-mesityl-3,4,5,6-tetrahydropyrimidin-1-ium), was also prepared, however its coordination chemistry was not studied due to the inherent instability of the resulting free C^N^C ligand.},
	keywords = {Chromium, N-heterocyclic carbene, nickel, Oligomerization, Pincer},
	author = {Papangelis, Evangelos and Pelzer, Katrin and Gourlaouen, Christophe and Armspach, Dominique and Braunstein, Pierre and Danopoulos, Andreas A. and Bailly, Corinne and Tsoureas, Nikolaos and Gerokonstantis, Dimitrios Triantafyllos}
}
