Stoichiometry controlled self-assembly of tri- and octa-nuclear palladium–yttrium complexes

Abstract

Palladium complexes with template-centred, bidentate bis-phosphine donors were prepared in a one-step process via base-assisted condensation of a ditopic catechol phosphine 1 (LH₂) with simple yttrium and palladium salts. It was found that the assembly of either one or two Pd-bisphosphine units on one template was possible in a controlled way by adjusting the stoichiometric ratio of the reactants. Thus, reaction of YCl₃, (cod)PdCl₂, and 1 in a 1 : 4 : 2 molar ratio produced a complex of composition [Y(H₂L₂Pd)(L₂Pd)(dmf)]Cl whereas reaction of the same reactants in 1 : 2 : 1 molar ratio gave a polynuclear assembly [O(YL₂Pd)₄(dmf)₄H]Cl₃. Both products were characterised by single-crystal X-ray diffraction studies and spectroscopic data (NMR, ESI-MS) which indicated that the assemblies found in the crystalline state persist also in solution.