Thioxanthates

The alkali-metal salts of the thioxanthates are formed by a method analogous to that used for xanthates. Alkali-metal mercaptides react with carbon disulfide to form thioxanthate salts (25)... 

A number of iron(III) xanthates and thioxanthates have been prepared (1). The structure of the predominantly low-spin [Fe(Rxant)a] (R = Et, or SBu) complexes show features (246, 252) of coordination about the iron atom that are significantly different from those of [Fe(Bu2dtc>3], and it is estimated that there is 10-30% of double-bond character in coordinated S2CX (X = OR, or SR), which is appreciably... 

The dithioacid family of ligands includes dithiocarbamates (R2N CS2 ), xanthates (RO-CS2 ), thioxanthates (RS CS2 ) and dithiocarboxylates (R CS2 ), which have been described in CCC(1987, Section 47.8.10).1 The ligands are prepared by addition of a suitable nucleophile to the carbon center in CS2, usually in the presence of a base. It has been established for some decades that they bind to Co almost exclusively as bidentate chelates, including S-donors acting as bridging ligands in dinuclear systems. 

Several complexes containing the W2S3 and W203 structural units have been prepared with thioxanthates and dithiocarbamates.178,179,180 Whether these have structures similar to the analogous molybdenum complexes is yet to be determined. 

Substituted dithioformate anions as ligands R C(S)S are usually called dithiocarbamates (R = R2N), alkyl and aryl dithiocarbonates or xanthates (R = RO), alkyl and aryl trithiocar-bonates or thioxanthates (R = RS). Dithioacid anions (R = alkyl, aryl) have been rarely used as ligands of nickel(II) because of their instability. Structural properties of selected nickel(II) complexes with substituted dithioformate, dithiolene and related ligands are shown in Table 90. 

A reaction typical of the thioxanthate derivatives is the CS2 elimination in very mild conditions with the formation of stable dimeric species with mercapto bridges (equation 210).2097-2100 Conversely, reaction (211) represents CS2 insertion into [(cpd)Ni(SEt)PBu3] to produce an ethylthioxanthate complex2100 where the ethylthioxanthate anion acts like the J COEt- anion in the complex jfcpd)Ni(S2COEt)Ph3].2101 Insertion reactions have also been reported to occur with PhNCS.2102... 

In the presence of CS2 and base, piperazine forms a bisdithiocarbamate, which is isolated as the bispiperazinium salt (252). Reaction of CS2 with cysteine in the presence of ammonia gives the dithiocarbamate—thioxanthate, which can be isolated as the triammonium salt (253) (Fig. 2). 

Fig. 2. The dithiocarbamate-thioxanthate ligand derived from the reaction of cysteine with carbon disulfide (2S3).

Differences in E% values between thioxanthate complexes and dithioacid complexes for equivalent processes have been related to the superior electron-... 

The spectra of the thioxanthate complexes (351) are qualitatively similar to those observed for the dithioacid derivatives (520), where efficient mixing of ligand 77 and the metal dx orbital has been suggested to account for the absence of transitions of pure d-d origin. 

The structure of the monomeric low-spin (2.46 BM, room temp.) Fe(f-BuSXant)3 complex has been determined (406) (Table XIX). The coordination geometry of the iron atom is a distorted octahedron of sulfur atoms contributed by the three chelating thioxanthate ligands. The structure of the low-spin (/ieff = 2.7 BM) Fe(EtXant)3 complex has been found to contain a distorted octahedral FeS6 core (340). 

Carbon disulfide elimination (Eq. 55) appears to be a general reaction of the thioxanthate complexes (153). 

RSXant Alkyl or aryl trithiocarbonate anion (thioxanthate) (RS-CSS)-... 

---