Synthesis, reactivity and characterization of mono-, bi- and tri-nuclear Schiff-base palladacycles with aromatic N-heterocycles

Reactions of mu(2)-Chloro bridged cyclometallated Pd(II) complexes [Pd{(4-R) C6H3CH=NC6H3-2,6-i-Pr-2}(mu-Cl)] (2) (R = H, OMe) with aromatic N-heterocycles such as 1-methylimidazole, 4,4'-bipyridyl (bpy), 1,2-bis(4-pyridyl)-ethene (bpe), 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (bpt) and 2,4,6-tris-(4-pyridyl)-1,3,5-triazine (tpt), generated mononuclear complexes [Pd{(4-R)C6H3CH=NC6H3-2,6-i-Pr-2}(L)(Cl)] (L = 1-methylimidazole, R = H, OMe), binuclear complexes [Pd{(4-R)C6H3CH=NC6H3-2,6-i-Pr-2}(Cl)](2)(mu-Y) (R = H, OMe; Y = bpy, bpe, bpt) and trinuclear complexes [Pd{(4-R) C6H3CH=NC6H3-2,6-i-Pr-2}(Cl)](3)(tpt) (R H, OMe). In contrast, the reaction of mu(2)-Chloro bridged cyclometallated Pd(II) complexes [Pd{(4-R) C6H3CH=NC6H3-2,6-i-Pr-2}(mu-Cl)](2) (R = H, OMe) with 2 equiv of AgNO3 and followed with bpy, bpe, bpt to produce binuclear cyclometallated Pd(II) nitrato complexes [Pd{(4-R) C6H3CH=NC6H3-2,6-i-Pr-2}(ONO2)](2)(mu-Y) (R H, OMe; Y bpy, bpe, bpt). Treatment of [Pd{(4-R)C6H3CH=NC6H3-2,6-i-Pr-2}(Cl)](3)(tpt) (R = H, OMe) with an excess AgNO3 produced trinuclear cyclometallated Pd(II) nitrato complexes [Pd{(4R)C6H3CH=NC6H3-2,6-i-Pr-2}(ONO2)](3)(tpt) (R H, OMe). All these complexes were fully characterized by FT-IR, NMR spectroscopy, elemental analysis and/or X-ray crystallography. (C) 2012 Elsevier B.V. All rights reserved.