Bismuthines

Very small quantities of bismuthine are obtained when a bismuth-magnesium alloy, BijMgj, is dissolved in hydrochloric acid. As would be expected, it is extremely unstable, decomposing at room temperature to bismuth and hydrogen. Alkyl and aryl derivatives, for example trimethylbismuthine, Bi(CHj)3, are more stable. 

Volatile hydrides, except those of Periodic Group VII and of oxygen and nitrogen, are named by citing the root name of the element (penultimate consonant and Latin affixes. Sec. 3.1.2.2) followed by the suffix -ane. Exceptions are water, ammonia, hydrazine, phosphine, arsine, stibine, and bismuthine. 

For the deterrnination of trace amounts of bismuth, atomic absorption spectrometry is probably the most sensitive method. A procedure involving the generation of bismuthine by the use of sodium borohydride followed by flameless atomic absorption spectrometry has been described (6). The sensitivity of this method is given as 10 pg/0.0044M, where M is an absorbance unit the precision is 6.7% for 25 pg of bismuth. The low neutron cross section of bismuth virtually rules out any deterrnination of bismuth based on neutron absorption or neutron activation. 

Bismuthine. Bismuthine [18288-22-7] BiH, is a colorless gas, unstable at room temperature, but isolatable as a colorless Hquid at lower temperatures. Owing to its instabiUty and difficulty of preparation, no mote than a few hundred milligrams of the pure compound have been available for any single study. Vapot-ptessute data from —116 to —43°C have been determined, and by extrapolation, a normal boiling point of +16.8° C has been indicated AH, calculated from the same data, is 25.15 kj/mol (6.01 kcal/mol) (7). 

The existence of bismuthine was first demonstrated by using a radioactive tracer, Bi (8). Acid treatment of a magnesium plate coated with Bi resulted in the hberation of a volatile radioactive compound. In subsequent experiments, magnesium bismuthide [12048-46-3], Mg Bi, was treated with acid the yield, however, was only one part of bismuthine for every 20,000 parts of bismuth dissolved. Attempts to prepare bismuthine by reduction of bismuth trichloride with a borohydride have not been particularly successful. Experimental quantities ate best prepared by disproportionation of either methylbismuthine [66172-95-0], CH Bi, or dimethylbismuthine [14381-45-4], C2H. Bi (7) ... 

At room temperature bismuthine rapidly decomposes into its elements. The rate of decomposition increases markedly at higher temperatures (8). Bismuthine decomposes when bubbled through silver nitrate or alkafl solutions but is unaffected by light, hydrogen sulfide, or 4 sulfuric acid solution. There is no evidence for the formation of BiH, though the phenyl derivative, (C H BU, is known. The existence of BiH would not be anticipated on the basis of the trend found with other Group 15 (V) "onium" ions. 

CgH BiBr2, and diphenylbromobismuthine [39248-62-9] C22H2QBiBr, respectively, with lithium aluminum hydride or sodium borohydride at low temperatures yielded only black polymeric substances of empirical formula C H Bi (33). It has been claimed (34) that dimethylbismuthine and diphenylbismuthine can be used as cocatalysts for the polymerisation of ethylene (qv), propylene (qv), and 1,3-butadiene. The source of these bismuthines, however, was not mentioned. 

A number of tertiary bismuthines have been prepared by the iateraction of a sodium diaryl- or dialkylbismuthide and an alkyl or aryl haUde (50) ... 

This method is of particular value for the preparation of unsymmetrical tertiary bismuthines. 

There have been several reports of the formation of tertiary bismuthines by the action of free radicals on metallic bismuth. One method of generating the radicals iavolves cleavage of ethane or hexafluoroethane ia a radiofrequeacy glow discharge apparatus the radicals thus formed are allowed to oxidize the metal at — 196°C (53). Trimethylbismuthiae and tris(trifluoromethyl)bismuthine [5863-80-9], C BiF, have been obtained by this procedure. 

Other methods of preparing tertiary bismuthines have been used only to a limited extent. These methods iaclude the electrolysis of organometaUic compounds at a sacrificial bismuth anode (54), the reaction between a sodium—bismuth or potassium—bismuth alloy and an alkyl or aryl haUde (55), the thermal elimination of sulfur dioxide from tris(arenesulfiaato)bismuthines (56), and the iateraction of ketene and a ttis(dialkylainino)bismuthine (57). 

The reaction of tris(trifluoromethyl)bismuthine with chlorine, bromine, or iodine, however, has been found to yield the corresponding bismuth trihahde and trifluoromethyl hahde (61) ... 

All three carboa—bismuth boads of trihen zylhismuthine [99715-52-3], C2 H2 Bi, (64) and triphenylbismuthine (65) can be cleaved by alkafl metals. Under some conditions, however, tertiary bismuthines react with sodium or potassium to yield secondary bismuthides. Thus a number of sodium dialkylbismuthides have been obtained by the iateraction of a trialkylbismuthine and sodium ia Hquid ammonia (66—69) ... 

The secondary bismuthides discussed herein are useful for preparing several types of organobismuth compounds, eg, tertiary bismuthines and dibismuthines. 

Although trialkyl- and triarylbismuthines are much weaker donors than the corresponding phosphoms, arsenic, and antimony compounds, they have nevertheless been employed to a considerable extent as ligands in transition metal complexes. The metals coordinated to the bismuth in these complexes include chromium (72—77), cobalt (78,79), iridium (80), iron (77,81,82), manganese (83,84), molybdenum (72,75—77,85—89), nickel (75,79,90,91), niobium (92), rhodium (93,94), silver (95—97), tungsten (72,75—77,87,89), uranium (98), and vanadium (99). The coordination compounds formed from tertiary bismuthines are less stable than those formed from tertiary phosphines, arsines, or stibines. 

Tertiary bismuthines appear to have a number of uses in synthetic organic chemistry (32), eg, they promote the formation of 1,1,2-trisubstituted cyclopropanes by the iateraction of electron-deficient olefins and dialkyl dibromomalonates (100). They have also been employed for the preparation of thin films (qv) of superconducting bismuth strontium calcium copper oxide (101), as cocatalysts for the polymerization of alkynes (102), as inhibitors of the flammabihty of epoxy resins (103), and for a number of other industrial purposes. 

Halobismuthines, Dihalobismuthines, and Related Compounds. Chloro-, dichloro-, bromo-, and dibromobismuthines are best prepared by the reaction of a tertiary bismuthine and bismuth trichloride or tribromide (7,43,45,46,104—107) ... 

In 1996, we started more detailed investigations on group 13/15 compounds containing the heavier elements of group 15, Sb and Bi, focussing on the synthesis of aluminum and gallium stibines and bismuthines. At the same time. Wells et al. also began to prepare M—Sb adducts and heterocycles (M = B, Ga, In). These studies, which are the object of this review, resulted in... 

The acid-base interaction in group 13-stibine and -bismuthine adducts seems to be very weak as is indicated by mass spectroscopic studies, which never showed the molecular ion peak but only the respective Lewis acid and Lewis base fragments. The extreme lability in the gas phase may also account for the fact that there are only very few reports on thermodynamic data of group 13-stibine or bismuthine adducts in the literature. Therefore, multinuclear NMR spectroscopy and single crystal X-ray diffraction are the most important analytical tools for the characterization of such adducts. 

In contrast to these trends observed for the stibine adducts, the H-NMR spectra of the bismuthine adducts R3M—BiR without exception show almost the same chemical shifts due to the organic groups as the starting trialkylalanes, -gallanes and -bismuthines, again indicating very weak acid-base interactions in solution. 

Reliable information on the thermodynamic stability of group 13/15 adducts is usually obtained by gas phase measurements. However, due to the lability of stibine and bismuthine adducts in the gas phase toward dissociation, temperature-dependent H-NMR studies are also useful for the determination of their dissociation enthalpies in solution [41b], We focussed on analogously substituted adducts t-BusAl—E(f-Pr)3 (E = P 9, As 10, Sb 11, Bi 12) since they have been fully characterized by single crystal X-ray diffraction, allowing comparisons of their thermodynamic stability in solution with structural trends as found in their solid state structures. 

Additional studies on R3AI—Bi(Tms)3 (R = Me 13, Et 14) showed the extreme lability of alane-bismuthine adducts toward dissociation in solution. Their H-NMR spectra at ambient temperature only show one resonance due to the Al—R groups, while at -70 °C two resonances of the A1—R groups in a... 

Up to now, fifteen group 13-stibine R3AI—SbR and four group 13-bismuthine adducts R3AI—BiR3 have been structurally characterized by single crystal X-ray diffraction studies. Their central structural parameters are summarized in Table 5. Structures 1-4 show the solid state structures of four representative adducts. 

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