A comparative study of cyclometallated palladium(II) compounds with terdentate [C,N,S] pincer ligands -: Crystal and molecular structure of [Pd{4-MeC6H3C(Me)=NNC(=S)NHMe}(PPh3)] and [Pd{4-MeOC6H3C(H)=N[2-(SMe)C6H4]}(Cl)]

Treatment of the thiosemicarbazone ligands 4MeC(6)H(4)C(Me)=NN(H)C(=S)NHMe (a), 4-MeC6H4C(N(4)e)= NN(H)C(=S)NHEt (b), and 4-MeC6H4C(Me)=NN(H)C(= S)NHPh (c) with K-2[PdCl4] produced the tetranuclear palladium(II) compounds [Pd[4-MeC6H3C(Me)=NNC(=S)NHMe}](4) (1a), [Pdl(4)-MeC6H3C(Me)=NNC(=S)NHEt}](4) (1b), and [Pdl(4)-MeC6H3C(Me)=NNC(=S)NHPh}](4) (1c) with deprotonation of the NH group. Treatment of thiosemicarbazones 4-MeOC6H4C(H)=NN(Me)C(=S)NH2 (d) and 3-MeOC6H4C(H)=NN(Me)C(=S)NH2 (e) with K-2[PdCl4] gave the mononuclear palladium(II) compounds [Pd[4-MeOC6H3C(H)=NN(Me)C(=S)NH2}(Cl)1 (1d) and [Pd{3-MeOC6H3C(H)=NN(Me)C(=S)NH2}(Cl)] 1e). Treatment of the Schiff base 4-MeOC6H4C(H)=N[2-(SMe)C6H4] (f) with Li-2[PdCl4] afforded [Pd{4-MeO6C6H3C(H)=N[2-(SMe)C6H4)](Cl)](1). All the ligands are terdentate through the [C,N,S] atoms and the Pd-S bond formed is sufficiently strong to tolerate treatment with nucleophiles without bond cleavage. Treatment of la, 1b, and 1c with triphenylphosphane gave the mononuclear species 2a, 2b, and 2c, which upon treatment with hydrochloric acid resulted in the 1:1 electrolytes 3a, 3b, and 3c, with NH and C=S groups. Coordination of PPh3 to Pd in If was achieved by treatment of the compound with sodium perchlorate, followed by the nucleophile in a 1:1 molar ratio, to yield 2f. The crystal structures of compounds 2a and If are described.