Bismuth, dibismuthine

Dibismuthines tend to be thermally unstable. Thus tetramethyldibismuthine [82783-70-8] C4H22Bi2, decomposes at 25°C to yield trimethylbismuthine and metallic bismuth (66) ... 

Dibismuthines are very sensitive to oxidation. Thus tetramethyldibismuthine fumes ia air, and tetraphenyldibismuthine ia toluene solution rapidly absorbs oxygen. Under controlled conditions, dibismuthines react with chalcogens resulting ia cleavage of the bismuth—bismuth bond and iasertion of a chalcogen atom (105,138,140—142) ... 

Selenium-bismuth bonds are formed in the mutual cleavages of dibismuthines and diselenides (equation 69).218 This particular compound is stable at -30 °C, unlike the tellurium analogue. At room temperature the compound disproportionates to give the diseleno derivative (equation 70). Similar behaviour was noted in the analogous sulfur compounds (Section 28.17.2.1). 

Inclusion of bismuth atoms in heterocyclic ring complexes has been actively investigated for a number of years. Complexes of the type (17), for example, l-phenyl-2,5-dimethylbismole, have been sought for comparison with pyrrole derivatives and for information about the degree of aromaticity in its heavier analogs. Compound (17) is prepared via the addition of 2(Z),5(Z)-dilithio-3,4-dimethylhexa-2,4-diene to PhBil2 in 28% yield. This heterocycle is converted to the dibismuthine in the standard fashion treatment of (17) with Na in liquid NH3 followed by addition of 1,2-dichloroethane. 

Dibismuthines are very labile they react readily with free radicals, electrophilic and nucleophilic reagents, which all cleave the Bi-Bi bond. Some dibismuthines are thermolabile tetramethyldibismuthine decomposes at 25°C quantitatively into trimethylbismuthine and bismuth metal. The half-life of this dibismuthine is approximately 6 h in a dilute benzene solution [82OM1408]. Tetraphenyldibismuthine [83CC507] and 2,2, 5,5 -tetramethyl-bibismole are stable up to 100°C [920M2743]. 

Thus, the thermal decomposition of tetramethyldibismuthine in the presence of bromotrichloromethane may take place via the following chain mechanism, (i) Tetramethyldibismuthine decomposes first into two dimethyl-bismuth radicals, (ii) These radicals react with bromotrichloromethane to form bromodimethylbismuthine bromide and a trichloromethyl radical, (iii) The trichloromethyl radical reacts with the dibismuthine to form dimethyl(trichlor-omethyl)bismuthine and dimethylbismuth radical. The termination step is the self-combination of the trichloromethyl radicals. In fact, the major product of the reaction is bromodimethylbismuthine bromide and the second product is dimethyl(trichloromethyl)bismuthine. Trimethylbismuthine, hexachloro-ethane and tetrachloroethylene are also formed in smaller quantities [830M1859]. 

The majority of Group 9 stibide and bismuthide complexes reported to date are cobalt derivatives [113,197,198]. Calderazzo and coworkers demonstrated that Co CO)g undergoes facile insertion into distibines and dibismuthines to afford their corresponding organostibide (66) and bismuthide (67) complexes (Scheme 15.20) [199]. Based on spectral data and parallel gas volumetric experiments, it was proposed that the antimony derivative is oligomeric, whereas the bismuth derivative is... 

---