Silanes methyl, rotational barrier

Some of the interesting features in silanes which are well reproduced by the calculations include the rotational barriers (T7 kcal mole-1 in methylsilane as compared with 2-9 kcal mole-1 in ethane, and correspondingly low numbers for other methyl silanes). While the torsional function about the 2,3-bond in 1-sila-butane looks almost like that in butane, the corresponding function... 

The barriers to methyl group rotation in tetramethyl silane and dimethylselenane are 1.4 and 1.5 kcal/mol respectively ). Bond lengths are carbon-silicon, 1.94, carbon-selenium 1.94, carbon-tellurium 2.14 based on the sum of covalent radii ). 

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