Thioamides metal complexes

Thioacetamide, MeC(=S)NH2 (taa), is isoelectronic with thiourea which it resembles by acting as a unidentate S-donor ligand. Thiobenzamide, PhC(=S)NH2 (tba), behaves similarly. Both thioamides form stable complexes with (b) class and borderline metals. Thioacetamide forms the tetrahedral complexes [MX2(taa)2] (M = Fe, Co, Zn X = Cl, Br, I, NCS).47,153-157 The v(M—S) frequency is rather low, ranging from 255 to 230cm, .14s The Mossbauer spectra of FeX2(taa)2 PC = Cl, Br) are consistent with a tetrahedral configuration.158... 

A,TV-Dimethyl-A -phenylthiourea has been shown to coordinate to Rh111 as an N—S bidentate involving four-membered chelate ring formation.154 N-Substituted thioamides also may bond in this manner.155 156 l-Amidino-2-thioureas (44) may behave either as N—S or as N—N bidentates, with this donor choice being dependent mainly on pH and the nature of the metal ion.157 As N—S donors they are known to stabilize lower oxidation states.158 As part of a study on Mo—S-containing complexes as models for redox-active molybdoenzymes, Dilworth et al. have shown that some p-(substituted)phenylhydrazines may coordinate as N—S bidentates in three different ways to one metal atom.159 The three diazenido, diazene and hydrazonido forms vary in their degree of deprotonation and therefore their anionic nature. 

Ligands (53) and (54) (L) form the complexes FeL X2 (X = Cl. Br. or I). for which spectral data suggest square-pyramidal structures.241 I.IO-Phenanthroline-2-carbo-thioamide and its -phenyl-derivative form both mono- and bis-ligand complexes with iron(u). which exhibit temperature-dependent spin-equilibria. In the monoligand complexes the metal atom is believed to be six-co-ordinate.242... 

The work that has been published on this polymerization shows it to be quite specific. Heavy metal ions such as silver and cadmium yield complexes that decompose spontaneously to the metallic sulfides 24). Attempted polymerization of bis(thioamides) of higher diacids led to formation of metallic sulfides in the case of adipic, pimelic, and terephthalic bis(thioamide) (22). However, malonic bis(thioamide) does yield polymer (22). Apparently, the six-membered ring that is formed can exist in this case [14], although it is less stable than the five-membered ring [8] (5,22,23). The rings that are required for polymer formation from the higher bis(thioamides) are apparently excluded, and the reaction forms metal sulfides instead. 

The increase in electrophilicity of coordinated ligands commonly leads to more favorable hydrolysis reactions. There are many reports on hydrolysis reactions of coordinated carboxamides, halogenated alkylamines, Schiff bases, thioamides, nitriles, etc. For example, thiourea and thioacetamide complexes of platinum metals decompose on heating in basic solution with formation of the corresponding metal sulfides, Eq. 1.26 and 1.27 ... 

Reacts with nitriles with the formation of thioamides. Forms many metal- and organometal-complexes, and is hence used in flotation technology. Pale-yellow cryst. (Et20). Sol. alkalis, CCI4. Mp 55-57°. 1.77 (7%... 

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