Formation of polynuclear palladium complexes with the benzimidazole-2-thiolate anion

Abstract

The reactions of palladium(II) salts with 2-mercaptobenzimidazole (HL) and its 5,6-difluorinated derivative (HLF) were investigated. In the presence of hydrochloric acid, PdCl2 and K2PdCl4 react with HL and HLF in the ethanol—water and acetonitrile—water systems to form the mono-nuclear dicationic complexes [Pd(HL)4]Cl2 (1) and [Pd(LF)4]Cl2 (2). In the absence of HCl, the reactions afford the tetranuclear complex Pd4[(L)2(μ3-S,N-(L))2(μS,N-(L))4] (3). The reaction of triethylamine with an ethanolic solution of 3 leads to degradation of 3 and the formation of the lantern-type dinuclear complex Pd2[(μ2-(L)4] (4), in which the palladium atoms are in the nonequivalent coordination environment, PdN4 and PdS4. The reaction of K2PdCl4 with HL or HLF in the THF—water or acetonitrile—water systems (for the reaction with HLF) in the presence of Et3N produces the lantern-type dinuclear complexes Pd2[(μS,N′-(L3))4] and Pd2[(μ-S,N′-(LF))4] (5), in which the metal atoms are in the equivalent coordination environment (cis-PdN2S2).