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Reactivity of Thiosemicarbazides with Redox Active Metal Ions: Controlled Formation of Coordination Complexes versus Heterocyclic Compounds
Author(s) -
LópezTorres Elena,
Dilworth Jonathan R.
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200801446
Subject(s) - chemistry , counterion , deprotonation , ligand (biochemistry) , medicinal chemistry , oxidative coupling of methane , reactivity (psychology) , metal , coordination complex , solvent , methanol , inorganic chemistry , oxidative addition , redox , salt (chemistry) , metal ions in aqueous solution , organic chemistry , ion , catalysis , medicine , biochemistry , receptor , alternative medicine , pathology
Careful metal selection : Control of the reaction conditions of Cu II and Sn IV with Me 2 NNHCSNHPh permits the selective synthesis of metal complexes or a range of heterocyclic compounds generated by the oxidative coupling of two thiosemicarbazides (see figure).The reactions of 1,1‐dimethyl‐4‐phenylthiosemicarbazide (LH) with Cu II and Sn IV have been investigated. If THF or methanol is used as solvent with Cu II , oxidative cyclisation and coupling are observed, yielding a 1,2,4‐thiadiazole or a 1,3,4‐thiadiazolium salt. SnI 4 is also able to induce oxidative coupling of two thiosemicarbazide ligands, yielding 1,2,4‐thiadiazolium or 1,2,4‐triazolium salts, with I 3 − as the counterion, depending on the reaction conditions. By contrast, reaction of LH with SnI 4 in acetone yields a 1,3‐thiazolium salt, with I − as counterion. Reaction with Cu II salts or SnI 4 in basic media leads to the formation of metal complexes containing two deprotonated thiosemicarbazide ligands. In the reaction of CuCl 2 in water in the presence of acid a complex containing two neutral ligands is obtained. Reactions with SnCl 4 are not able to induce ligand cyclisation, although a coordination compound with two neutral ligands was isolated from methanol.