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Treatment of 4-MeOC 6 H 4 C(Me)dNN(H)C(dS)NHMe (1), with potassium tetrachloropalladate gave the tetranuclear compound [Pd{4-MeOC 6 H 3 C(Me)dNNdC(S)NHMe}] 4 (2), with the ligand as terdendate [C,N,S]. Reaction of 2 with the diphosphines Ph 2 PCH 2 PPh 2 (dppm), Ph 2 PC(dCH 2 )PPh 2 (vdpp), and Ph 2 PC(CH 2 ) 2 PPh 2 (dpcp) gave the mononuclear complexes [Pd{4-MeOC 6 H 3 C(Me)dNNdC(S)NHMe}( L)] (L = dppm-P, 3; dpcp-P, 4; vdpp-P, 5) with the diphosphine ligand binding in a monodentate fashion. Compounds 3-5 may bond systematically to a second metal atom, palladium or platinum, through the noncoordinated phosphorus atom and the sulfur atom of the thiosemicarbazone moiety to give the dinuclear compounds 6-10, thus behaving as bidentate P,S-palladacycle metaloligands. All the compounds have been characterized by elemental analysis, and by IR and NMR spectroscopy; and the crystal and molecular structures of 1, 2, 6-10 have been determined by X-ray crystallography. Inter-and intramolecular hydrogen bonding in the solid results in crystal self-organization leading to chains and/or layers in the molecular array.

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The reaction of the thiosemicarbazone ligands 1‐(COMe)‐3‐[C(H)=NN(H)C(=S)NHR]C8H5N, (R = H a, Me b, Et c) with potassium tetrachloropalladate in an ethanol/water mixture led to the new tetranuclear palladium(II) compounds [Pd{1‐(COMe)‐3‐[C(H)=NN=C(S)NHR]C8H4N‐k3C5,N,S}]4 (R = H 1a, Me 1b, Et 1c) which contain six‐membered metallacycles. The thiosemicarbazone ligands in these complexes are terdentate through the C, N, and S atoms and are deprotonated at the NH group. The Pd–S bond formed is sufficiently strong to undergo reactions with nucleophiles without bond cleavage. Reaction of 1a and 1b with 1,2‐bis(diphenylphosphanyl)ethane (dppe) gave the dinuclear species [{Pd[1‐(COMe)‐3‐{C(H)=NN=C(S)NHR}C8H4N]}2(μ‐Ph2P(CH2)2PPh2)] (R = H 2a, Me 2b). The molecular structure of complex 1b has been determined by X‐ray diffraction analysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)