Typical bond distances

Typical C—Cl bond distances in crystals were derived by Allen and coworkers172 using the same procedure described for fluorine compounds. The substructures chosen for the chlorine compounds (Table 29) differ slightly from those for fluorine derivatives. Since 

TABLE 29. Typical C—C bond distances (in pm) in crystals, standard deviations a and number, n, of observations in various substructures 

C—Cl distances are less affected by electronegative substituents than C—F bond distances, no distinction between C and X = H, C, N or O will be made for chlorine compounds. 

5 -Pentachloro-4-methoxybiphenyl tris(2,4,6-trichlorophenyl) methyl radical 

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In Fig. 5.12, the radial distribution functions for the neutral iron-atom are plotted. It is evident that the orbitals with the same main quantum number occupy similar regions in space and are relatively well separated from the next higher and next lower shell. In particular, the 4s orbital is rather diffuse and shows its maximum close to typical bonding distances while the 3d orbitals are much more compact. 

The second pathway for the reaction B11(A3) + H2 leads to complex B21, where the N-H bonds are trans to each other. It takes the now familiar path addition of H2 across the Zr2-N2 bond, where the original hydrogen atoms are in the N -H and Zr -H2 bonds. TS B20 for this reaction involves four atoms, Zr2, N2, H3 and H4, in the active regions and has the typical bond distances N2- H4=1.369A, H3-H4=1.033A, H3-Zi2 2.219A and Zr2-... 

It can be seen that inside the octahedral coordination of the Ir(III) centre an unusual peroxide bond forms between the terminal oxygen atom (04) of coordinated dioxygen and the carbon atom (C7) of the semiquinone ligand. In fact, the 0-0 distance of the oxygen molecule (1.47 A) is within the typical bond distance of peroxide coordination (1.49 A). 

X-ray structural analysis of 2,2-dimethyl-3-phenyl-l-methylenecyclopropane tungsten pentacarbonyl reveals an octahedral complex with characteristic W—C bond distance of 238 pm. The typical bond distances within the organic ligand are 138 (complexed C=C), 148 (proximal C—C), 154 (distal C—C) pm, compared e.g. with 140, 148 and 154 pm, respectively, for the Feist s ester iron complex analogue (see above). 

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. 

The overall bonding scheme for a carbon-carbon double bond includes both o and 7t bonds (and their empty antibonding counterparts) and is also shown in Figure 3.13. Carbon-carbon double bonds are quite short, with a typical bond distance being 1.33 A. 

Dipole-dipole coupling 2-30 kHz (at typical bond distance) No Intemuclear distance and orientation H, N, Through-space distances Translational and rotational motions... 

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