1,3,5‐Triazapentadienes as Chelating Ligands: 1,2,4‐Triphenyl‐1,3,5‐triaza‐pentadiene Complexes of Cobalt( II ), Nickel( II ), Palladium( II ), Copper( II ) and Zinc( II )

Abstract 1,2,4‐Triphenyl‐1,3,5‐triazapentadiene (1a), prepared from benzamidine and N‐phenylbenzimidoyl chloride, was treated at room temperature with CoCl2, Ni(NO3)2, Na2PdCl4, CuCl2 and ZnCl2 to form the corresponding six‐membered 1:1 chelate complexes 1a·CoCl2, 1a·Ni(NO3)2, 1a·PdCl2, 1a·CuCl2, and 1a·ZnCl2. In the solid state 1a·Ni(NO3)2 forms infinite linear chains, bridged by nitrate ions. From 1a and Cu(OTf)2 a 2:1 copper complex was obtained [(1a)2·Cu(OTf)2]. In all cases a proton shift from nitrogen atom N1 in the free ligand to N3 in the complex was observed. All complexes were completely characterized including X‐ray crystallography. Quantum chemical DFT calculations indicate that triazapentadiene is a better ligand for ZnCl2, PdCl2 and CuCl2 compared to ‐diimines and N‐acylamidines. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)