Diorganyls

On treatment with an equivalent amount of (Et2N)3P, thiotelluroxide 67a is reduced to give telluroazocine 65 in almost quantitative yield, which can be converted into telluroxide 68 by the usual procedures for a diorganyl telluride to telluroxide transformation. It is worth noting that when treated with Lawesson reagent, the telluroxide 68 forms thiotelluroxide 67a, whereas diaryl telluroxides are reduced by this reagent to diaryl tellurides. 

The use of sterically bulky ligands to provide kinetic stability to compounds of the heavier group 2 elements has become widely practiced, and has facilitated the synthesis of diorganyl complexes of various types. Advances in the organometallic chemistry of bonded compounds of calcium, strontium, and barium have been reviewed. 

Selected mono- and di(A,A-diorganyl-imidazol-2-ylidene)gold(i) complexes have been investigated for their antibacterial activity. Positive effects against Staphylococcus and Enterococcus bacteria, Escheria coli, and Pseudomona aeruginosa were encountered in particular with the A-substituents being mesityl or benzyl (Equation (51)).278... 

Under aprotic conditions, prototropic transformations of thiols are relatively slow, so one can observe distinct waves of the oxidation of the protonated form and of its parent base [19, 20]. Normally, the oxidation of thiols (aliphatic, aromatic, and heteroaromatic) affords diorganyl-disulfides. So various aliphatic and aromatic thiols are easily converted into the corresponding disulfides upon oxidation in MeOH/MeONa with the yields ranging... 

Since diorganyl sulfides and sulfoxides can be mutually interconverted electrochemi-cally [222] (for the oxidation of sulfides to sulfoxides and further to sulfones, see Sect. 9.2.3), sulfoxides take an intermediate position between sulfides and sulfones (Eq. 27). 

Sections 3.1-3.3 outline the principal preparative methods of diorganyl tellurides and ditellurides, organyltellurium trichlorides and diorganyltellurium dichlorides, which were the first classes of compounds investigated at the beginning of tellurium organic chemistry. 

Diorganyl tellurides have low molecular mass and are colourless or yellowish liquids with an unpleasant and penetrating odour. Dimethyl teUuride is a metabolite of tellurium and tellurium compounds in a variety of living organisms, including humans. Higher dialkyl tellurides and most diaryl tellurides are solids with low melting points (diphenyl telluride is a liquid). 

Diorganyl tellurides are soluble in common organic solvents. 

Because of the above-mentioned organoleptic properties, it is recommended that contact between dialkyl tellurides and the skin is avoided, and that, in general, all work involving diorganyl tellurides is performed under a well-ventilated hood. 

Diorganyl tellurides, compounds with two organic groups linked to a tellurium atom, constitute the most abundant and famihar class of organic tellurium compounds. The organic groups, of the most differentiated types, can be identical or different, giving rise to symmetrical or unsymmetrical tellurides. 

Actually, the method of choice for the preparation of organyl tellurolate anions is the reduction of diorganyl ditellurides with reducing agents. 

From diorganyl ditellurides or arenetellurenyl halides and organometallic reagents... 

A different approach to unsymmetrical diorganyl tellurides, in which an electrophilic tellurium species is used, involves the nucleophilic attack of organomagnesium or organo-lithium reagents to diorganyl ditellurides. 

Unsymmetrical diorganyl tellurides (general procedure). A solution of the ditelluride (2 nunol) in THE (30 mL) is treated dropwise at 0°C under N2 with Br2 (0.32 g, 3 mmol)... 

Three main routes have been well established for the preparation of diorganyl ditellurides (1) The reaction of sodium ditelluride with alkylating or arylating agents. 

This is the most direct route to diorganyl ditellurides and therefore parallels the ronte leading to diorganyl tellnrides, snbstitnting sodium telluride for sodium ditelluride. Sodium ditelluride is prepared employing, with the appropriate ratio of the elements, methods analogous to those described for sodium telluride. 

The Grignard route to diorganyl ditellurides suffers from lack of generality and the mechanism of the oxidation seems to be uncertain. Alkylmagnesium halides demonstrate lack of reactivity towards elemental tellurium/ whereas aryhnagnesium halides in ether as the solvent furnish a mixture of ditellurides and tellurides. Satisfactory results are obtained by tellurium insertion in aryhnagnesium halides in THF followed by oxidation before or after aqueous work-up. ... 

The reduction of organyltellurium trichlorides, which are the primary products of several reactions involving tellurium tetrachloride (see Section 3.5.1), is a useful and general method for the preparation of diorganyl ditellurides. 

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