Iodomethane, bond length

The simplest iodoalkane, CH3I, has been studied repeatedly by MW and ED (Table 43). The re value for the C—I distance from a combined MW/IR investigation and the rg value which is reported in a recent ED analysis of the entire series of the iodomethanes CH I, n = 1 to 4, are in perfect agreement. The gas-phase studies for the methanes with two or more iodines were performed at 360 K for CH2I2, at 400 K for CHI3 and at 425 K for CI4. Within the combined experimental uncertainties the C—I bond distances remain constant for mono-, di- and triiodomethane and increases by ca 3 pm in carbon tetraiodide. As in the case of carbon tetrachloride and tetrabromide, this increased bond length in CI4 can be rationalized by steric repulsions between the iodine atoms. The large steric requirement of... 

The alkenylsilane 98 reacts with iodine to afford the sUalactone 99, with elimination of iodomethane, in good yield (Fig. 35) [81]. This unexpected process involves the mild oxidative cleavage of a silicon-carbon bond which should otherwise be stable. The silicon-carbon bond is activated by hypervalency induced by intramolecular coordination of the carbonyl oxygen to the silicon atom. This is supported by the observation that the O-C braid length is shorter than that of the sum of the van der Waals radii (3.35 A) in the X-ray crystal structure analysis of 98. The TBP value [82] is 20%, meaning that it is not a perfect trigonal bipyramidal structure but is on the way... 

---