Mixed Triply and Doubly Bridged Dinuclear Palladium(II) Cyclometalated Compounds. Crystal and Molecular Structures of [1,3-{Pd[2,3,4-(MeO)3C6HC(H)NCH2](μ-O2CMe)}2C6H4] and [1,4-{Pd[2,3,4- (MeO)3C6HC(H)NCH2](Cl)}2C6H4(μ-Ph2P(CH2)3PPh2)

Abstract

Reaction of the Schiff base ligand 1,3-[2,3,4-(MeO)3C6H2C(H)NCH2]2C6H4 (1) with palladium(II) acetate in toluene gave the doubly cyclometalated complex [1,3-{Pd[2,3,4-(MeO)3C6HC(H)NCH2](μ-O2CMe)}2C6H4] (2), in which the two palladium atoms are intramolecularly bonded by acetato bridging ligands. The crystal structure of 2 is given. Reaction of the Schiff base ligand 1,4-[2,3,4-(MeO)3C6H2C(H)NCH2]2C6H4 (6) with palladium(II) acetate under similar reaction conditions yielded the cyclometalated complex [1,4-{Pd[2,3,4-(MeO)3C6HC(H)NCH2](μ-O2CMe)}2C6H4]n (7), probably of polymeric nature. Reaction of 2 and 7 with aqueous sodium chloride gave the chloro-bridged complexes [1,3-{Pd[2,3,4-(MeO)3C6HC(H)NCH2](μ-Cl)}2C6H4]2 (3) and [1,4-{Pd[2,3,4-(MeO)3C6HC(H)NCH2](μ-Cl)}2C6H4]2 (8), respectively, after a metathesis reaction. Treatment of complex 2 with Ph2P(CH2)3PPh2 (dppp) in a 1:1 molar ratio gave the dinuclear cyclometalated complex [1,3-{Pd[2,3,4-(MeO)3C6HC(H)NCH2](OAc)}2C6H4(μ-Ph2P(CH2)3PPh2)] (4), in which the metal atoms are bonded by the diphosphine ligand. Treatment of the chloro-bridged complex 3 with dppp in a 1:2 molar ratio gave the dinuclear cyclometalated complex [1,3-{Pd[2,3,4-(MeO)3C6HC(H)NCH2](Cl)}2C6H4(μ-Ph2P(CH2)3PPh2)] (5), with the palladium atoms intramolecularly bridged by the diphosphine. The complex showed a fluxional behavior in solution, with the cyclometalated moieties adopting a cis/trans arrangement. Reaction of the chloro-bridged complex 8 with dppp in a 1:2 molar ratio yielded the mixture of complexes [1,4-{Pd[2,3,4-(MeO)3C6HC(H)NCH2](Cl)}2C6H4(μ-Ph2P(CH2)3PPh2)] (9) and [1,4-{Pd[2,3,4-(MeO)3C6HC(H)NCH2](Cl)}2C6H4(μ-Ph2P(CH2)3PPh2)]2 (10), of which only 9 was isolated pure. Compound 9 showed a structure and solution behavior similar to those of 5; however, the structure of 10 was not unambiguously established. The crystal structure of 9 is also reported.