Polynuclear cyclometallated palladium (II) complexes derived from potentially hexadentate Schiff base ligands.: Crystal structures of [(Cl)Pd{Me2NCH2CH2N=(H)C}C6H2{C(H)=NCH2CH2NMe2}-Pd(Cl)] and [{(Ph2PCH2CH2)2PPh-P,P,P}Pd{Me2NCH2-CH2N=(H)C}C6H2{C(H)=NCH2CH2NMe2}- Pd{(Ph2PCH2CH2)2PPh-P,P,P)][Cl]2

The oxidative addition reaction of 1,4-(C=N(H)CH2CH2Me2)(2)-2,5-Cl2C6H2 with tris(dibenzylideneacetone)dipalladium(0) in benzene gave the doubly cyclometallated compound [(Cl)Pd{Me2NCH2CH2N=(H)C}C6H2{C(H)=NCH2CH2NMe2} Pd(Cl)] (1) with each palladium atom C,N,N' bonded to the ligand. Treatment of 1 with thallium acetylacetonate gave the dinuclear cyclometallated complex 2 with two chelating acetylacetonate ligands. Reaction of 1 with tertiary monophosphines in a I-phosphine 1:2 molar ratio gave dinuclear cyclometallated complexes 3-7, in which the palladium-NMe2 bond has been broken, whereas treatment of 1 with silver perchlorate, followed by reaction with PPh3 in a l-phosphine 1:2 molar ratio gave cyclometallated complex 4 where the ligand remains C,N,N' bonded and the chloride ligand has been substituted by triphenylphosphine Treatment of 1 with tertiary diphosphines leads to dinuclear compounds 8, 10 and 11, whilst previous treatment of 1 with silver perchlorate followed by the diphosphine 1,4-bis(diphenylphosphino)butane (dppb) in a l-diphosphine 1:1 molar ratio yielded the tetranuclear complex 9. Reaction of 1 with the tertiary triphosphine bis(2-diphenylphosphinoethyl)phenylphosphine in 1:2 molar ratio gave the complex [{(Ph2PCH2CH2)(2)PPh-P,P,P} Pd{Me2NCH2CH2N=(H)C}C6H2{C(H)-NCH2CH2NMe2}Pd{(Ph2PCH2CH2)PPh-P,P,P}][Cl](2) (12) in which both palladium atoms are pentacoordinated. The crystal structures of 1 and 12 are described. (C) 2000 Elsevier Science B.V. All rights reserved.