Thiocarbenes

Alkylation of thioacyl ligands provides a route to thiocarbene complexes. Faraone and co-workers have prepared iridium thiocarbene complexes 20 and 21 by methyl iodide addition to Ir(I) thiocarbonyl... 

A similar strategy can be applied to intramolecular systems for the synthesis of cyclic alkenyl sulfides37 (Scheme 25). Instead of chloroalkyl sulfides 82, dithioacetals 83 can be used more effectively as the precursor of thiocarbenes... 

In Figure 2.2 the most important synthetic approaches to alkoxy- or (acy-loxy)carbene complexes from non-carbene precursors are sketched. Some of these strategies can also be used to prepare amino- and thiocarbene complexes. These procedures will be discussed in detail in the following sections. In addition to the methods sketched in Figure 2.2, many complexes of this type have been prepared by chemical transformation of other heteroatom-substituted carbene complexes. Because of the high stability of most of these compounds, many different reactions can be used to modify the substituents at C without degrading the carbon-metal double bond. The generation of heteroatom-substituted carbene complexes from other carbene complexes will be discussed in Section 2.2. 

The thiocarbene complex [(CO)5WC(SMe)Me] has been prepared by the reaction of [(CO)sWC(OMe)Me] with HSMe at room temperature. The position of the v(C )) stretching frequencies, the energy barrier for rotation about the C—S bond, the ionization potential, and the dipole moment of the... 

The strong jt-bonding character in compounds of pentacarbonyl (group-VI metal) (0) with thiocarbene can be seen from the metal-carbon bond distances. For chromium compounds they were found to be ... 

Thietanes are formed by intramolecular cyclization of thiocarbenes (110) (75BCJ1490), on pyrolysis of the copolymer of sulfur, tetrafluoroethylene and thiocarbonyl fluoride (111) (69CC1274), and upon electrolysis or base treatment of dithione (112) (67JOC1562,78JOC1980, 79JCR(S)320>. 

The second example shows that such a reaction need not always lead to an uncharged system. If, instead of thiocarbene complexes, amino-carbene complexes are treated with hydrogen halides, products of saltlike character are isolable (66). One finds the halogen at the metal and the hydrogen at the removed carbene ligand, and one obtains iminium halo-genopentacarbonylmetalates ... 

Na2[Cr(CO)5] reacts with C12CS in THF to produce Cr(CO)5(CS) in ca. 5% yield. This thiocarbonyl complex reacts with Ph3P to produce trans-[Cr(CO)4-(CS)PPh3] and with primary amines (RNH2) to produce a thiocarbene, which... 

The alkoxy substituent in 12 may be replaced by thio or amino groups upon treatment with thiols and amines to give thiocarbene 13 and aminocarbene complexes 14, respectively. 

Even Lewis acid adducts of the acyl metalate 11 (Section 8.3.1.1, Scheme 8) proved effective in generating benzannulation products. The reaction of a trimethylsilyloxy chromium carbene complex with 3-hexyne to give the respective semi-silylated hydroquinone tricarbo-nylchromium complex in 35 % yield [30a] and the use of titanoxycarbene complexes [30b] constitute such examples. Thiocarbene complexes form hydrothioquinones in a Lewis acid supported benzannulation reaction [32]. 

Thiazadiphosphole, synthesis with phosphaalkenes, 18-19 Thiocarbene complexes, synthesis, 224-225... 

A number of reactions of organothiols with complexes of alkoxycar-benes, isocyanides, or thiocarbonyls, leading to thiocarbene complexes, have been reviewed (4,125,126). Further related examples include the conversion of a chlorocarbene to a dithiocarbene by reaction of the ruthenium complex 154 with RSH (R = Me, p-tolyl) or HSCH2CH2SH to give the dithiocarbene compounds 155 and 156 (82). 

The formation of the thione complex 211 involves the coupling of two thioformaldehyde units, addition to the carbyne carbon of 210 to form a thiocarbene ligand, sulfur insertion into the metal-carbene bond, and... 

The reaction between the thiocarbene complex 413 and (Cp3)2C=NC(0)R (R = Ph, P-FQH4) leads to scission of the carbene ligand and transfer of the nucleophilic SMe fragment to the electrophilic center of the acylamine. Protonation, effected either by the rest of the carbene or the solvent, results in a thioether derivative (414) (249). 

The reactions of nucleophiles mostly concern thiocarbene and thiocar-byne complexes some have been reviewed by Angelici ei al. (4). 

Complexes of type 458 can be obtained by the addition of nucleophiles, R [M] (MeLi, MeMgBr, CsHuMgBr, PhMgBr, Me2CuLi, Bu2CuLi, Me2CuLi) to cationic thiocarbene complexes of type 457 (R = H or Me, R = Me or Ph) (277). 

Kreissl and Keller demonstrated sequential transfer of two [SMe]" groups to the metal-carbon triple bond of 131 to afford the thiocarbene... 

---