Pd(II)–N-heterocyclic carbene complexes of annelated ligand: Synthesis, characterization, and catalytic activity

• Published in: Inorganica Chimica Acta 2015-11, Vol.438, p.58-63
• Main Authors: Rana, Bidyut kumar, Seth, Saikat Kumar, Bertolasi, Valerio, Mahapatra, Pradip Kumar, Al-Deyab, Salem S., Dinda, Joydev
• Format: Article
• Language: English
• Subjects: Annelated carbene; N-heterocyclic carbene; Pd(II)–NHC; Suzuki coupling
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2015.08.025

Synthesis, structural characterizations and catalytic activities of two novel Pd(II)–NHC complexes based on C, N donor annelated NHC are highlighted. [Display omitted] •Annulated NHC ligand.•Pyridine wingtip NHC.•Pd(II)–NHC complexes.•Suzuki coupling reaction. The annelated imidazolium salt 1-methyl-2-(pyridin-2-yl)imidazo[1,5-a]pyridin-4-ylium hexaflurophosphate (1·HPF6) has been synthesized by via formylative cyclization of the corresponding Schiff base 2-acetylpyridyl-N-(2-pyridyl)methylamine using standard conditions followed by anion metathesis with NH4PF6. Reaction of 1·HPF6 with silver oxide and palladium chloride led to the formation of the palladium complex [Pd(1)2Cl]PF6, 2. Subsequent reaction of 2 with AgPF6 gave the palladium complex [Pd(1)2][PF6]2, 3. The complexes have been fully characterized by different spectroscopic techniques and finally the solid state structures of 2 and 3 have been determined by single crystal X-ray diffraction studies. The catalytic activities of 2 and 3 have been tested in the Suzuki–Miyaura coupling reactions of several activated para-functionalized aryl bromides with phenyl boronic acid to find that 2 is slightly more efficient than 3.