Tetrakis tetrahedrane

Accordingly, we first synthesized bis(supersilyl)tetrabromodisilane (tBu3Si)SiBr2 SiBr2(SitBu3) (Scheme 16). It transforms by reaction with supersilyl sodium into tetrakis(supersilyl)tetrasila-tetrahedrane in high yields, shown at the right-hand bottom of Scheme 16 [2]. 

Next, some reactions of hexakis(trifluoromethyl)benzvalene will be discussed. This compound is very stable as mentioned before and its olefinic double bond reacts as an efficient dienophile. The difference in the reactivity between unsubstituted benzvalene and the hexakistrifluoromethylated derivative is that the former is nucleophilic while the latter is highly electrophilic. Thus, the former does not react with usual 1,3-dienes, in contrast to the latter. Here, mainly describe our results of the several reactions of hexakis(trifluoromethyl)benzvalene which were designed for the synthesis of tetrakis(trifluoromethyl)tetrahedrane. 

In 1976, Chapman repeated our experiment at 8K and reported that tetrakis-(trifluoromethyl)tetrahedrane is formed. Some time later, Masamune and his coworkers detected cyclobutadiene in the IR and UV spectrum but not the tetra-hedrane 9S),... 

Tetrakis(trimethylsilyl)tetrahedrane (12) is a colorless crystalline solid, mp 202°. Unlike tetra-7-butyltetrahedrane (5), wliich melts at 135° with isomerization to the... 

Tetralithiotetrahedrane is apparently unknown. The synthesis of a fully-characterized monolithio tetrahedrane, tris(trimethylsilyl)tetrahedraityllithimn (13), was reported in 2003 by Sekiguchi and Tanaka [41], who prepared it by reacting tetrakis(trimethylsilyl)tetrahedrane 12 [32, 33] with methyllithium. 

Calculations on tetra(f-butyl)tetrahedrane, tetrakis(trimetltylsilyl)tetrahedrane, and the parent tetrahedrane. 

Let ns apply these principles to tetra-i-butyltetrahedrane, tetrakis(trimethylsilyl) tetrahedrane, and tetrahedrane itself. Unreferenced calcrrlations are by the author, and some of these results are strmmarized in Table 6.1. Note that calcrrlations designed to address kinetic stability directly, by examining transition states for interconversion of diradicals (below), seem to be limited to the parent molecule. 

Table 6.1 Energies from B3LYP/6-31G calculations on tetrahedranes and cyclobutadienes (by the author, using Gaussian 03). Note that for the tetra-t-buty and the tetrakis(trimethylsilyl) systems the tetrahedrane is calculated to lie below the cyclobutadiene in energy, but for the parent molecules the tetrahedrane is calculated to lie above the eyelobutadiene...

As stated above, B3LYP/6-31G calculations place tetrakis(trimethylsilyl)tetra-hedrane about 37kJ mol below the cyclobutadiene [33]. This calculated energy difference would have made one reasonably confident of the greater thermodynamic stability of the tetrahedrane. 

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