Geometry and the degree of aromatic stabilization

Of the three possible disilabenzene isomers, ortho-21, meta-22 and para-11, only 11 is known experimentally and was observed in a matrix36. The published calculations on disilabenzenes are all at relatively low levels of theory (i.e. they used a relatively 

Using the appropriate bond-separation reactions, the UF/3-21G aromatic stabilization energies are calculated to be 47.2, 36.4 and 22.5 kcal mol-1 for 22,11 and 21, respectively, compared to 59.0 kcal mol-1 for benzene503 thus the meta-, para- and ortho-isomers have 80, 62 and 38% of the aromaticity of benzene. The different orders of the thermodynamic stability of the three isomeric disilabenzene and of their aromatic stabilization energies 

FIGURE 4. The -molecular orbitals of disilabenzenes (a) 1,2-disilabenzene (21) (b) 1,3-disilabenzene (22) (c) 1,4-disilabenzene (11). The orbital coefficients given are of the outer valence -atomic orbitals (at HF/3-21G). Reproduced by permission of Elsevier Sequoia S.A., from Reference 50a 

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