Synthesis and characterization of N-heterocyclic carbene palladium complex and its application on direct arylation of benzoxazoles and benzothiazoles with aryl bromides

Author： Arslan Hakan Ozdemır Ismaıl Vanderveer Don Demır Serpıl Cetınkaya Bekır

Publisher： Taylor & Francis Ltd

ISSN： 0095-8972

Source： Journal of Coordination Chemistry, Vol.62, Iss.16, 2009-08, pp. : 2591-2599

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Abstract

A mixed-halogen bis(1-(4-tert-butylbenzyl)-3-(2, 4, 6-trimethylbenzyl)-1H-benzo[d]imidazol-2-ylidene) palladium(II) complex, trans-[Pd(Cl0.7Br0.3)2(C28H32N2)2], has been synthesized and characterized by elemental analysis, 1H-NMR, 13C-NMR, and IR spectroscopy, and single crystal X-ray diffraction. The palladium in the mononuclear complex is four-coordinate in a square-planar configuration with two carbenes of two benzo[d]imidazole rings and two halides. The two halides are disordered between Br and Cl, with the Cl: Br ratio approximately 0.7 : 0.3. The angles C1-Pd1-Br1, 88.63(11)° and C1i-Pd1-Br1i, 91.37(11)° (i: 1-x, 1-y, 1-z) in the coordination sphere are very close to the ideal value of 90°. The Pd-X distance is slightly longer than other carbene derivative Pd-Cl single bond distances and slightly shorter than Pd-Br single bond distances. These results agree with the Cl/Br disorder at the halogen position. The palladium-carbene complex was tested as a catalyst in the direct arylation reaction of benzoxazoles and benzothiazoles with aryl bromides.