Chalcogen reaction, insertion

In general, dipnictines react cleanly with sulfur, selenium, or tellurium to afford corresponding chalcogen (Ch) insertion products of general formula RjPn-Ch-PnRj. Such reactions occur with... 

The chalcogen atoms readily insert into Li-C or Mg-C bonds and this method is widely used to prepare in situ these reagents for further reactions. 

The first examples of a chalcogen insertion into a transition metal-carbene bond were reported in 1981. Stirring solutions of the pentacarbonyl-(diarylcarbene)tungsten complexes 39 in pentane in the presence of solid sulfur afforded the thioketone complexes 40 [Eq. (8)].171 The reaction rate increased considerably when pentane was replaced by CS2 as the solvent due to the higher solubility of elemental sulfur in CS2. 

The reaction of tetrachlorodisilane with chalcogenation reagents is one of the synthetic methods to bis-nor-adamantane or double-decker type compounds. When a solution of di-terf-butyltetrachlorodisilane 66 in THF is refluxed together with one equivalent of lithium sulfide or stirred with lithium selenide at room temperature, the tetra(ferf-butylsilicon)pentachalcogenides 67 and 68, respectively, are formed (Scheme 18)6. Each pentachalcogenide exhibits one resonance of a ferf-butyl group in the H and 13C NMR spectra. Most likely, the bis-nor-adamantane derivatives 69 and 70 are initially formed. Insertion of a sulfur or selenium atom into one of the two strained Si—Si bonds would then lead to the observed products. 

The stable silylenes react, however, with water and alcohols, by straightforward insertion into O—H bonds. Silylenes 59, 61 and 62 all react with methyl iodide, inserting into the C—I bond. Examples of these reactions are shown for 59 in Scheme 18. Compounds 59 and 61 also react with elemental chalcogens. For 61 with Ss, Ses or Te 37°, and for 59 with... 

Aryl iodides, in Grignard reagent preparation, 9, 35 Aryl isocyanides, chalcogen—chalcogen additions, 10, 752 Aryl isonitriles, in insertion reactions, 1, 106-107 Aryl ketones, via intramolecular G—H functionalizations,... 

Sulfur and selenium heterocycles have also been prepared by reaction of zirconium-benzyne complexes with the elemental chalcogens. In these reactions, chalcogens insert into both of the zirconium-carbon bonds (Scheme 7).53-55 Interestingly, neither para-bromo norpara-dimethylamino substituents in 65 interfere with their conversion to 66 (60-80% yields).54 Complexes 66 react further with mono- and bifunctionalized electrophiles (Scheme 7) to yield ort/io-dichalcogenated benzenic compounds 67-69. 

Further reactions of P-hydridocyclotriphosphazenes (See Section IV,E) have been described. They undergo insertion reactions with aldehydes, ketones, isothiocyanates and electrophilic olefins. Addition of sulfur or oxidation with KMn04 gives thioxo-or oxo-cyclotriphos-phazene derivatives which are methylated at the chalcogen to afford methylthio- and methoxy- cyclotriphosphazenes (36). Hydridocyclo-phosphazenes can also be oxidized to give symmetric and unsymmetric bis(cyclotriphosphazenyl) oxides (35). 

Electrophilic attack at carbyne complexes may ultimately place the electrophile on either the metal or the (former) carbyne carbon, the two possibilities being related in principle by a-elimination/migratory insertion processes (Figure 5.39). The reactions of the osmium carbyne complex are suggestive of an analogy with alkynes. Each of these reactions (hydro-halogenation, chlorination, chalcogen addition, metal complexation see below) have parallels in the chemistry of alkynes. 

Chalcogens E (E = O, S, Se, Te) readily insert into the Ge—Li bond. For example, reaction of E with PhGeLi yields Ph3GeELi (E = O, S, Se, Te) ", Brook and Gilman found that triphenylgermyllithium was oxidized to Ph3GeOLi, and carbon dioxide could... 

Reaction of R2ln-InR2 (R = CH(SiMe3)2) with the chalcogen compounds can give the corresponding homoleptic compounds R2lnEInR2 (E = S, Se or Te) by insertion of... 

Relatively little is known of the chemistry of antimony rings compared to arsenic rings. The reactions of arsenic homocycles have been reviewed several times " . They include cleavage of the As—As bonds with halogens and insertion of chalcogens or unsaturated hydrocarbons and reductive cleavage with potassium metal. Representative examples are given in equations 15-18. 

Formal E (E = S or Se) insertion, sulfurization of organic carbonyls, and nucleophilic addition to coordinated organosulfur and organoselenium compounds are reviewed in this section. Reactions of HjS, HE , and in which the chalcogen atoms exhibit nucleophilic character, as well as new contributions to CEj chemistry, especially reactions with coordinated car-banions and dimerizations, also receive attention. 

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