COMPLEXES OF BINUCLEATING LIGANDS. XII. SYNTHETIC APPROACHES TO BINUCLEATING LIGANDS CONTAINING EITHER A BRIDGING THIOUREA COMPONENT OR A BRIDGING ALIPHATIC THIOLATE COMPONENT AND SOME COMPLEXES THEREOF

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Abstract
N,N′-di(p-tolylthiomethyl)ethylene thiourea, (L), the thiourea sulphur atom of which is a potential bridging centre, gave the cropper(I) derivatives, LCu2Cl2 and LCu3Cl3 · CH3CN. However, with silver(I) and palladium(II) L disintegrated, leaving the thiolate fragment coordinated to the metal. Synthetic approaches to a range of 1,5-bis(substituted thio)-pentane-3-thiol ligands incorporating a variety of donors at the termini of the thioether side arms were investigated but the only sequence which was developed to the stage where metal complexes could satisfactorily be generated involved the side arms ortho-S.C6H4 · NH2. The S-protected derivatives, 1,5-bis-(2 ' -aminophenylthio)-3-triphenylmethylthiopentane and 1,5-bis-(2 ' -aminophenylthio)-3-benzylthiopentane afforded accessible and convenient sources of the binucleating ligand 1,5-bis-(2′ -aminophenylthio)pentane-3-thiol. With palladium(II) the S-trityl derivative was smoothly S-deprotected at temperatures below 100° C but the S-benzyl derivative required temperatures as high as that of boiling DMF. The binucleating ligands discussed here appear, at this stage, less versatile with regard to ready synthesis and structural modification and of generally less potential usefulness than analogous systems, described elsewhere,2 involving a bridging thiophenoxide component.