From dibismuthines

Tetramethyldibismuthine reacts with butyllithium in hexane to generate a mixture of trialkylbismuthines of the type Me Bu3 Bi (n = 0-3) along with lithium dimethylbismuthide [830M1859]. 

Organobismuth(in) compounds with Bi-group 14 element bonds 

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Nine other thermochromic distibines have been reported. All show a yellow melt, but the solid colors range from deep yellow to violet-blue. Seven thermochromic dibismuthines are known. The liquid colors are all red while solid colors are variable. The thermochromic distibines and dibismuthines are listed in Table II (7,10,17a,21,23-41) along with the melting points and colors of the crystals. Nonthermochromic dibismuthines are collected in Table III (20,29,32,42). 

On crystallization, nonthermochromic distibines and dibismuthines show little visual change. The solid colors of two nonthermochromic distibines (8 and 9) and two nonthermochromic dibismuthines (45 and 46) have been characterized by diffuse reflectance. In each case, only very modest changes in the absorption maxima were observed and between solid and solution. On the other hand, the intense colors shown by the solid phases of the thermochromic distibines are red shifted by 200-250 nm from their solution phase maxima (see Table IV) (7,25,29,33,34,37, 38b,40). The dibismuthines are red shifted even further. There is complete correspondence between dibismuthines and the analogous distibines, with the dibismuthines being red shifted by around 100 nm (see Fig. 1). 

Fewer structural data are available for dibismuthines. Published structures include only the thermochromic tetrakis(trimethylsilyl)dibismu-thine (37) (57) and the nonthermochromic tetraphenyldibismuthine (46) (42) although some data from an unpublished structure of tetramethyl-... 

No theoretical treatment is available for dibismuthines. However, the qualitative features of the band structures of the thermochromic dibismuthines can be anticipated from the Hoffmann model for the corresponding distibines. Thus, the substitution of Bi for Sb is unlikely to affect greatly the ligand v orbitals. But the trg orbital will likely be raised to reflect the weaker metal-metal bond (28). A smaller band gap is predicted, as is observed. 

Sodium metal (0.23 g, 10 mmol) was added piecewise to a well stirred mixture of chlorodi-phenylbismuthine (3.58 g, 10 mmol) in liquid ammonia (100 ml). By warming to 0°C, ammonia was evaporated from the resulting green-black solution. The residue was taken up in toluene (25 ml) and filtered off. On addition of methanol (10 ml), the dibismuthine separated from the solution as air-sensitive red crystals (1.55 g, 45%) [830M1859]. 

To a solution of iododiphenylbismuthine (8.806 g, 17.97 mmol) in THF (250 ml), dicyclopen-tadienylcobalt(II) (3.368 g, 17.83 mmol) dissolved in the same solvent was added dropwise at room temperature over a period of 5 min. After stirring for 10 min, the precipitated dicyclo-pentadienyl iodocobalt(III) was filtered off and the orange solution was evaporated to dryness under reduced pressure at room temperamre. The residual solid was recrystallized from dry hot ethanol (600 ml). The dibismuthine obtained as orange needles was collected by filtration and dried in vacuo. Yield 80% [88IC3730]. 

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