Direct functionalization of sp(2) C-H bonds via ortho diarylation of 2-pyridyl benzene with arylbromides was achieved using ruthenium(II) catalysts containing a RuCl2(NHC) unit and generated from [RuCl2(arene)](2) and two types of NHC precursors, pyrimidinium and benzimidazolium salts, in the presence of Cs2CO3. DFT calculations from RuCl2(NHC)(2-pyridylbenzene) show that a proton abstraction mechanism, on cooperative actions of both the coordinated base and the Ru(II) center, is favoured via a 13.7 kcal mol(-1) exothermic process affording an orthometalated intermediate with a 2.009 angstrom Ru-C bond.