Thiocarbonate ligands

Thiocarbonates are readily formed by the action of SH" on CS2 in alkaline solution, and numerous yellow salts containing the planar ion are known. Heating CS3 with S affords orange tetrathiocarbonates, which have the structure [S3C—S—S]2. The free acids can be obtained from both these ions as red oils, stable at low temperatures. Other thiocarbon ligands are shown in Fig. 7-11. They have an important place in coordination chemistry, where they are found bound to many metal atoms in species such as Ni(C3S5)2, CpN QSs),63 and (p-cymene)2Ru2Cl2(C4S6).M... 

This addition of CS2 under reducing conditions represents a facile, in situ synthesis of [ 83] thiocarbonate ligands that are difficult to prepare by conventional methods. 

The substituted ferrocenes 757 are widely used as metal-ligand systems. These compounds have a great variety of chelating groups (R) (1-diketones (a) [458], semicarbazones and thiosemicarbazones (b) [458], azomethines and their analogues (c) [458-462], oximes (d), carbonic, thiocarbonic (e), and amino acids (f) [458] ... 

The crystal structure of the dithioacetylacetone (sacsacH) complex of cobalt(n), Co(sacsac)2, shows it to be monomeric square planar,164 in marked contrast to the acacH analogue. Pyridine 2-thiol (LH), which can exist as the thione tautomer (31) forms Co(LH)2X2 (X = Cl, Br, or I) complexes these contain the ligand bonded through the sulphur, as evidenced by the presence of a v(N—H) vibration in the i.r. spectra.165 Morpholine 4-thiocarbonic acid (32) also appears to be S-bonded in the CoL2X2 complexes (X = Cl, Br, or I), since the v(C=S) frequency is lowered upon co-ordination.166 The electronic spectra of the CoL2C12 complexes (L = thiourea, A-phenylthiourea, and TViV -diphenylthiourea) have been recorded.167... 

Alkyl(aryl) thiocarbonates (xanthates) are (9-alkyl(aryl) esters of the hypothetical dithiocarbonic acid, HSC(S)OH.174,175 These esters are unknown in the free state and only their alkali metal salts, M[S2COR], are readily available, and stable enough to be used as starting materials for metal complexes. Alkyl(aryl) dithiocarbonates (xanthates) were discussed in CCC (1987) and continued to be used as ligands, with some interesting new results being reported. 

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