Thiometalate

Transition metal thiometalates properties and significance in complex and bioinorganic chemistry. A. Muller, E. Diemann, R. Jostes and H. Bogge, Angew. Chem., Int. Ed. Engl., 1981, 20, 934-955 (227). 

An unusual cage structure with two six-membered rings was formed by reaction of thiometalates with silver salts. Extraction of an aqueous solution of either (NH WS 320 or... 

DISCRETE THIOMETALATE IONS—PROPERTIES, ELECTRONIC STRUCTURE AND... 

Heterometallic clusters from thiometalate ligands by unit construction and the possibility of... 

DISCRETE THIOMETALATE IONS — PROPERTIES, ELECTRONIC STRUCTURE AND REACTIVITY1... 

The chalcogenometalates are prepared either by reactions in the solid state from the constituent elements themselves or by the reaction of H2S with an aqueous solution of the corresponding oxometalate. Several of the known thiometalates have only been isolated in pure form or detected in solution within the last 20 years. The preparation of selenometalates, and particularly that of the... 

For aspects of complex formation it is important to realize that thiometalates are not very stable in aqueous solution, especially at low pH. Their decomposition may be caused by hydrolysis to oxometalates, by intramolecular redox processes, or by their marked tendency to form sulfides. With molybdates and tungstates the stability decreases with increasing oxygen content and increasing electron density on the ligands. When they decompose in acid media, binary sulfides (or with selenometalates, selenides) such as MoS3 are formed. 

The consideration of the reactivity is necessary to understand the formation of homonuclear thiometalato complexes formed from MS4 species. M=S groups with w-bond contributions (e.g. in the thiometalates) can react with either nucleophiles (Nu equation 1) or electrophiles (E equation 2). 

While a great deal of research has been done on condensations of oxometalates in aqueous solutions, there has been little such work in the field of thiometalates. The condensation reactions subsequent to protonation of thiometalate ions take place at lower pH than those of the oxoanions, since the proton affinity of S is appreciably lower than that of O. Investigation of condensation behavior of thiometalate ions is more difficult, since various complex decomposition processes are also involved. For example, no definite condensation product has yet been isolated from an aqueous solution containing MoS2-. 

EH-SCCC-MO calculations on the diamagnetic polythiometalates M3XSg (X = O, S) also show that these can be described as coordination compounds of MIVX2+ with MS4- ligands. For instance, an occupied MO is about 50% localized on the central W atom, but owing to the appreciable (ca. 20%) participation of the outer orbitals of W atoms there is a clear metal-metal interaction comparable to the M -TM interaction in heteronuclear systems (TM = thiometalate).]... 

Table 1 Multimetal Complexes with Thiometalate Ligands (Averaged M—S and M [ M Distances in Ay ...

It is worth noting that one thiometalate ligand provides six bonds to Cu and Ag atoms in the cage structure compounds. 

Thiometalate ligands are coordinated via sulfur to soft cations such as Cu+, Ag+ and Au+. Thus, it has not yet been possible to prepare any compound of the structural type (c) with MOS3 ligands. Following this principle, using oxotrithiometalates, compounds with a cubane-like structure were deliberately prepared. 

This redox behavior is typical of complexes of first row transition metal ions chelated by two thiometalates and Table 2 shows data for many of these species. The following conclusions can be drawn on the basis of these data. 

Finally, the electrochemical data for the cobalt system enable evaluation of the effect on redox properties of the thiometalate ligands (TM) varying from M02S2- to MS2-. It is evident that an-increasing oxygen content of the ligand makes the reduction more difficult. 

Dithiete can be used as an oxidant for the thiometalates and oxythiometalates, and thus induced internal electron-transfer reactions provide an efficient method for synthesizing selected metal dithiolene and oxo-containing... 

Mo and W trisulfides themselves are prepared by thermal decomposition of the ammonium thiometallates, (NH4)2MS4 (M = Mo, W).18 Accordingly, direct decomposition of the ammonium thiometallates in H2 yields the MoS2 and WS2 nanotubes (Fig. 10).21 In addition to providing a direct method... 

In a similar reaction, [MoS 412 reacts with C4S5O, the monothiocarbonyl derivative of TPD, to give the same products as above, showing the preferential reactivity of the thiometalate for the dithio- versus the trithiocarbonate. It was also found that the tetrasulfido complex ZnS4(pmdta) (Section III. A) reacts with TPD to give Zn(S2C2S2CO)(pmdta) (189). 

---