Some palladium complexes of quadridentate ligands containing the deprotonated amide group

Abstract

The ability of palladium to promote the ionisation of amide hydrogen atoms is demonstrated by the preparation of a series of neutral complexes of quadridentate ligands containing two deprotonated amide groups. The other groups are either both primary amine, both secondary amine, or both thioether groups. The names of the ligands and the formulae of the complexes are NN′-di-(2-aminoethyl)malondiamide, Pd[CH₂(CO·N·CH₂·CH₂NH₂)₂],3H₂O, NN′-di-(3-benzylaminopropyl)oxamide, Pd(–CO·N·[CH₂]₃·NH·CH₂Ph)₂, NN′-di-(S-ethylmercaptoacetyl)-1,3-di-aminopropane, Pd[CH₂(CH₂·N·CO·CH₂·S·CH₂·CH₃)₂]. With ligands of general formula RNH·CO·CH₂·S·-[CH₂]_n·S·CH₂·CO·NHR, when R = H, n= 2 or 3, neutral complexes are formed, Pd{[CH₂]_n(S·CH₂·CO·NH)₂},-xH₂O (n= 2, x= 2; n= 3, x= 3). When R = CH₂·CH₂·OH, for steric reasons only one of the two amide groups can co-ordinate through nitrogen and the complexes formed are PdCl(HO·CH₂·CH₂·N·CO·CH₂·S·[CH₂]₂·-S·CH₂·CO·NH·CH₂·CH₂·OH) and {Pd(HO·CH₂·CH₂·N·CO·CH₂·S·[CH₂]₃·S·CH₂·CO·NH·CH₂·CH₂·OH)}⁺Cl^–.