C sp3 —I bonds

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 

Two MW investigations of iodine-substituted cyclohexane and adamantane apply several geometric constraints in the structure analyses which result in large values for the estimated experimental uncertainties for the C—I bond distances. The bond lengths of ca 216-217 pm correspond to that in ICHMe2 [216.7 (2) pm] and similar observations were made for C—Cl and C—Br bond lengths in monosubstituted unstrained saturated rings. 

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Crystal structures for some iodine-substituted compounds were selected from the CSD according to the same criteria applied for chlorine and bromine compounds, except that the number of iodine atoms [criterion (a)] was relaxed to > 1. This search resulted in 18 observations for C(sp3)—I bonds with a mean value of 216.6 pm and o = 2.0 pm. The individual values range from 212.3 to 220.6 pm. 34 observations were listed for C(sp2)—I distances with a mean value of 210.1 pm and a large standard deviation of 6.1 pm. The values range from 205.7 to 223.9 pm. The mean values of this sample are very close to the typical bond distances listed by Allen and Coworkers172. Table 46 lists C(sp3)—I and C(sp2)—I bond distances for some selected crystal structures. 

TABLE 46. C(sp3)—I and C(sp2)—I bond distances (in pm) in some selected crystal structures... 

Values are from References 24, 25, 27, 51 and 53. Those in italics are estimates, and / Me parameterize the bond moments of the X-C(sp2) and X-C(sp3) bonds, respectively i values reported as 0/1 take the value 1 when bonded to sp2-hybridized carbon and 0 when bonded to sp3-hybridized carbon. Dipole moments for alternating dienyl and polyenyl groups are assumed to be approximately equal to those for the 1- and 2-(l,3-butadienyl) groups. 

Murahashi S-I, Nakae T, Terai H, Komiya N (2008) Ruthenium-catalyzed oxidative cyana-tion of tertiary amines with molecular oxygen or hydrogen peroxide and sodium cyanide sp3 C-H bond activation and carbon-carbon bond formation. J Am Chem Soc 130 11005-11012... 

Amorphous carbon films may be broadly classified as (i) amorphous carbon films, a-C films, deposited from carbon-containing gases with low or zero hydrogen content [72] and (ii) hydrogenated carbon films, a-C H films, formed from hydrocarbon-containing gases [73,74]. Both types of film contain different amounts of sp2 and sp3 bonded carbon. The amount of sp2 bonded carbon can be estimated from X-ray absorption near edge spectroscopy,... 

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