Tetrachloromethane and silicon tetrachloride. Tetrachloromethane reacts with great difficulty with hydroxide ions, whereas silicon tetrachloride reacts vigorously with water alone. Chlorine's covalent radius is 99 pm, carbon's 77 pm, silicon's 118 pm. The silicon atom has accessible 'empty' d -orbitals, whereas carbon does not. The energy barrier to reaction is thus much larger than in the case of chloromethane with its small hydrogen atoms.
Tetrachloromethane is therefore difficult to hydrolyse.
This is due firstly to the higher degree of ionic character in the case of silicon tetrachloride, and probably also to non-bonded repulsions between the chlorine atoms in tetrachloromethane. This latter view is supported by the weakness of C-Cl in tetrachloromethane compared with the average value for this bond. It may be a true 5-covalent intermediate, an sp 3 d hybrid. The net result is the much faster hydrolysis of the silicon halide. CRC Press 1995.