Synthesis of terpyridine-containing Pd(II) complexes and evaluation of their catalytic activity

Herein, we prepare two terpyridine-containing Pd(II) complexes, [PdClL1]center dot solvent (A(1)) and [PdClL2] center dot 2H(2)O (A(2)) (L-1 = 4'-(4-carboxyl-phenyl)-2,2':6',2 ''-terpyridine, L-2 = 2,6-bis(2-pyrazinyl)-4-(4-carboxyl-phenyl)pyridine), from 4'-(4-cyanophenyl)-2,2':6',2 ''-terpyridine(L-1a)/2,6-bis(2-pyrazinyl)-4-(4-cyanophenyl)pyridine (L-2a) and Pd(II) acetate and characterise them by several instrumental techniques. A(1) and A(2) are shown to be good catalysts for the coupling of 2-iodobiphenyl with iodobenzenes to afford triphenylenes, which is known to involve dual C-H bond activation and double C-C bond formation. The obtained data suggest that the mechanism of A(1)-and A(2)-mediated coupling may be similar to the reference Pd catalysts, A(1) and A(2) are also suitable catalysts for this cyclization process. Study on this kind of complexes is of importance to the development of novel Pd-based catalysts and triphenylene synthesis techniques. (C) 2019 Elsevier B.V. All rights reserved.