Crown Ether Palladacycles as Metalloligands: Suitable Precursors for Tetranuclear Mixed Transition/Non-Transition Metal Complexes

Reaction of Pd(OAc)2 with the Schiff base ligands 2,3,4-(MeO)3C6H2C(H)═N-[9,10-(C8H16O5)C6H3] (a) and 2,3,4-(MeO)3C6H2C(H)═N[9,10-(C10H20O6)C6H3] (b) leads to the cyclometalated compounds [Pd{2,3,4-(MeO)3C6HC(H)═N-[9,10-(C8H16O5)C6H3]-C6,N}(μ-O2CMe)]2 (1a) and [Pd{2,3,4-(MeO)3C6HC(H)═N[9,10-(C10H20O6)C6H3]-C6,N}(μ-O2CMe)]2 (1b), respectively, via C−H activation. The metathesis reaction of 1a with aqueous tetrabutylammonium chloride gave the corresponding cyclopalladated dimer with bridging chloride ligands, 2a. Treatment of the dimer compounds with NaClO4, KClO4, NH4PF6, Pb(SCN)2, RbClO4, and Ba(ClO4)2 gave the corresponding products in which the cation (Na+, K+, NH4+, Pb2+, Rb+, Ba2+) was coordinated to the crown ether moiety. The structures of compounds 1a and 6a (a complex with one Na+ cation coordinated to each crown ether group) have been determined by X-ray single-crystal diffraction analysis.