Thiocarbonyl ligands

In this review, quantitative aspects of the structure and reactivity of these compounds are treated first. New developments in the fields of synthesis and reactivity are examined next. As a consequence of their relevance for the development of new materials23-27 and the possibilities they offer for analytical purposes, the number of studies in which thiocarbonyl compounds act as ligands of a variety of metal ions has increased in an almost explosive way. Recent reviews28-30 are also available on specific families of coordination compounds involving thiocarbonyl ligands. A concise survey of the present status of these studies is presented in the last section. 

Among the heterocyclic thiones, we present in Tables 20-25 the metal complexes of some of the thiocarbonyl ligands most widely used, which are represented in Figure 3. In these tables, data are given from 1988. In the case of copper, only complexes reported since Raper s review28 are given. 

FIGURE 3. Thiocarbonyl ligands involved in Tables 20-25 (a) pyridine-2-thione, (b) pyridine-4-thione, (c) pyrimidine-2-thione, (d) l,3-imidazoline-2-thione, (e) benz-l,3-imidazoline-2-thione, (f) l,3-imidazolidine-2-thione, (g) l,3-thiazoline-2-thione, (h) benz-1,3-thiazoline-2-thione, (i) 1,3-thiazolidine-2-thione, (j) 1,2,4-triazoline-3(5)-thione, (k) 1,2,3,4-tetrazoline-5-thione... 

CS)(PPh3)2RuCl3Ru(PPh3)2Cl] 0.115 both Ru atoms have distorted octahedral coordination. Ru—Ru = 3.35 A. Disorder prevented satisfactory delineation of thiocarbonyl ligand f... 

The thiocarbonyl ligand bonds to transition metals in seven different ways ... 

Roper and Town explain the conversion, with hydrogen, of an osmium-coordinated CS ligand in 94 to SMe in terms of successive hydride transfers from the metal to the thiocarbonyl ligand yielding first a thioformaldehyde complex and then a methanethiolate complex, 95 (95). Later this group... 

Functionalization of a thiocarbonyl ligand occurs during the nucleophilic attack on a cyclopentadienyl iron complex by aziridine. 

Other hand, electrophilic addition to thiocarbonyl ligands is a well-established method for the synthesis of thiocarbyne complexes (5). Doyle and Angelici synthesized the cationic thiocarbyne complex 42 according to Eq. 

TRI-ju-CHLORO-CHLOROTETRAKIS(TRIPHENYLPHOS-PHINE)DIRUTHENIUM(II) COMPLEXES WITH ACETONE CARBONYL AND THIOCARBONYL LIGANDS... 

Although, unlike carbon monoxide, CS does not exist under ordinary conditions, a number of complexes containing the thiocarbonyl ligand have been... 

Carbon monosulfide is not a stable molecule, but carbon monosulfide complexes (more commonly called thiocarbonyl complexes) are known for most of the transition metals. Because of the mstability of free CS, most CS complexes have been prepared by generation of CS from CS, Cl CS, or EtOC(S)Cl in the coordination sphere of the metal, as shown in Equations 2.5, 2.6, and 2.7. Thiocarbonyl ligands vibrate between 1160 and 1410 cm" free CS (in a matrix) vibrates at 1274 cm". A detailed analysis of force constants of mixed carbonyl and thiocarbonyl complexes indicates that the CS ligand can be a weaker or stronger TT-acceptor tiian CO. Seleno- and tellurocarbonyl complexes are also known. ... 

Electrophilic addition to the sulfur atom of terminal thiocarbonyl ligands is a well-established route to thiocarbyne complexes of Group VI metals [2, 18, 19]. A requirement for the success of this approach is that the thiocarbonyl ligand be bound to a very electron-rich metal centre, preferably in an anionic complex. A methyltellurocarbyne complex of tungsten, [L(CO)2W=CTeMe]... 

Little new chemistry of osmium thia-macrocycles has appeared, but both ruthenium and osmium [9]aneS3 complexes with thiocarbonyl ligands and their migratory coupling reactions have been investigated. ... 

However, MO calculations suggest that nucleophilic attack is not charge-controlled although it is not possible to predict the site of attack since too many closely spaced empty energy levels are associated with both acyl and carbonyl carbons. Similar calculations on [Cr(CO)6 C(OMe)Me ] indicate that the lowest unoccupied MO is localized on the carbene carbon and frontier orbital control predicts nucleophilic attack on the carbene carbon. The electron density on the sulphur atom of coordinated thiocarbonyl ligands, as indicated by v(C==S), is considered to control the reactivity towards electrophiles and only those with C—S stretching modes above 1200 cm have been found to react. ... 

Triangular array of Co atoms with a triple 47 bridging thiocarbonyl ligand. d(Co-Co) = 2.43 A. 

In mixed complexes containing carbonyl and thiocarbonyl ligands, nucleophilic attack at co-ordinated carbon could take place either at carbonyl-C or at thiocarbonyl-C. [Fe(A -C5H5)(CO)a(CS)]+ reacts with, for example, azide ion or hydrazine by attack of the nucleophile at the thio-carbonyl-C. On the other hand, methoxide ion attacks [Ir(CO)2(CS)-(PPh3)2]+ at the carbonyl-C. ... 

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