2015. 56, 5 UDC 548.73 CRYSTAL STRUCTURES OF TWO N-HETEROCYCLIC CARBENE-PALLADACYCLES H.M. Li1, X.Q. Li u 1, Z. Q. Wang2, W.J. Fu2, C. Xu 2 1College of Life Science, Luoyang Normal University, Luoyang, Henan, P. R. China 2College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang, Henan, P. R. China E-mail: xubohan@163.com Received December, 14, 2014 teractions are found in the crystals. <...> N-heterocyclic carbenes (NHCs) have become a paradigmatically new generation of strong -donor ligands and are successfully used in the palladium-catalyzed coupling reactions [ 1, 2 ]. <...> Among them, a combination of a palladacycle framework with highly donating and sterically demanding NHCs has been reported [ 3—8]. <...> In addition, NHCs have attracted increasing interest as ancillary ligands that opened new avenues for the design of emitting materials due to their excellent color purity and high stability [ 9—11]. <...> Recently, we have investigated fluorescent NHC-cyclopalladated 2-(4-ethylphenyl)pyrazine and 2-(4-methoxyphenyl)pyrazine complexes [ 12 ]. <...> As a part of our continuous research work, herein, the structures of two NHC [N,N-bis((1,3-di-4-methyl-phenyl)-imidazol)-2ylidene]-palladacycles are determined by single crystal X-ray diffraction. <...> Single crystals suitable for X-ray diffraction were obtained by recrystallization from a CH2Cl2-petroleum ether solution at room temperature. <...> Single crystal X-ray diffraction data of complex 1 and 2 were collected on a Xcalibur, Eos, Gemini diffractometer with graphite-monochromated Mo h radiation (y = 0.071073 nm). <...> In the final step of the crystal structure refinement, hydrogen atoms of idealized —CH2 and —CH3 groups were added and treated with the riding atom mode; their isotropic displacement factor was chosen as 1.2 and 1.5 times the preceding carbon atom, respectively. <...> Crystal data and experimental details of the structure determinations, selected bond distances and angles, and hydrogen bonding parameters are listed in Tables 1 and 2, respectively. <...> The X-ray diffraction data were deposited with the Cambridge Crystallographic Data Center (CCDC no. 1039124 for 1 and 1013221 for 2) and are available from the authors at www.ccdc.cam.ac.uk <...>