Direct oxidation of tertiary bismuthines

Lower trialkylbismuthines such as Mc3Bi are pyrophoric under atmospheric conditions. (PhCH2)3Bi also decomposes with a smoke in air [57CB1176]. Controlled oxidation of trialkylbismuthines with molecular oxygen [71CJC1747, 71JCS(C)1660], ferf-butyl hydroperoxide 

Tris(4-methylphenyl)bismuthine (0.482 g, 1 mmol) was added to a suspension of freshly prepared iodosobenzene (0.286 g, 1.3 mmol) in dry dichloromethane (30 ml) and the resulting mixture was sonicated at 35°C under argon on a commercial ultrasonic washing machine until the substrate was completely consumed (checked by TLC). After 2-3 h, the chalky suspension turned to a bright yellow solution of tris(4-methylphenyl)bismuthine oxide, which was quickly filtered through a Celite bed and used for further pmposes [94TL8197]. 

The physical properties of triorganylbismuthine oxides have not been examined quite so extensively. Goel et al. claim that triphenylbismuthine oxide has a five-coordinated bismuth center with a polymeric structure involving -Bi-O-Bi- units [72JOM(36)323]. 

Triphenylbismuthine oxide is a white solid which reportedly melts at 155°C and is moderately soluble in benzene, slightly soluble in acetonitrile but insoluble in chloroform and diethyl ether. The equivalent conductance of a 2 X 10 M solution in acetonitrile at 25°C is 1.5 ohm cm equiv . The molecular weight has not yet been determined due to its extensive 

The most characteristic property of the bismuthine oxides is their oxidizing ability to convert activated alcohols, triphenylphosphine and hydrazobenzene to the corresponding ketones, oxide and azo compound, respectively. However, thioanisole and methyl octyl sulfide remain intact even after prolonged stirring with bismuthine oxide at ambient temperature [94TL8197] (Section 5.2.4). 

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