The key role of sulfur in thiosemicarbazone compounds. Crystal and molecular structure of [Pd{4-MeOC6H4C(Me)NNC(S)NHPh}2]

The reaction of thiosemicarbazones 4-MeOC6H4C(H)NN(H)C(S)NHMe (a), 4-MeOC6H4C(H)NN(H)C(S)NHEt (b) and 4-MeOC6H4C(H)NN(H)C(S)NHPh (c), with Li2[PdCl4], K2[PdCl4] or Pd(AcO)2 leads to the tetranuclear palladium(II) compounds, [Pd{4-MeOC6H3C(H)NNC(S)NHMe}]4 (1a), [Pd{4-MeOC6H3C(H)NNC(S)NHEt}]4 (1b) and [Pd{4-MeOC6H3C(H)NNC(S)NHPh}]4 (1c); the ligands are terdentate through the [C, N, S] atoms and they are deprotonated at the –NH– group. Reaction of thiosemicarbazones 3-MeOC6H4C(H)NN(H)C(S)NHMe (d) and 3-MeOC6H4C(H)NN(H)C(S)NHEt (e), with Li2[PdCl4] or K2[PdCl4] gave the mononuclear palladium(II) compounds [Pd{3-MeOC6H4C(H)NNC(S)NHMe}2] (1d) and [Pd{3-MeOC6H4C(H)NNC(S)NHEt}2] (1e); the ligands are bonded only through the azomethine nitrogen and sulfur atoms. Treatment of thiosemicarbazone 4-MeOC6H4C(Me)NN(H)C(S)NHPh (f) with Li2[PdCl4] gave the tetranuclear compound [Pd{4-MeOC6H3C(Me)NNC(S)NHPh}]4 (1f), which upon treatment with bis(diphenylphosphino)methane, dppm in 1:2 molar ratio gave the dinuclear species [{Pd[4-MeOC6H3C(Me)NNC(S)NHPh]}2(μ-Ph2PCH2PPh2)] (2f). The recrystallization of 2f gave the chiral compound [Pd{4-MeOC6H4C(Me)NNC(S)NHPh}2] (3f). The molecular structure has been determined by single-crystal diffraction, showing O⋯H and S⋯H hydrogen bonding.