Covalent radii, for carbon

In Section 4 the data on bond lengths and strengths have been vastly increased so as to include not only the atomic and effective ionic radii of elements and the covalent radii for atoms, but also the bond lengths between carbon and other elements and between elements other than carbon. All... 

This value has been adjusted for a 0.105 A difference between sp and sp covalent radii of carbon. 

According to the different covalent radii of carbon and silicon (Chap. 2), the exchange of the Ci0 chain of decamethonium for a 9 atom chain of 7 carbon atoms and 2 silicon atoms with a C3SiCSiC3 sequence should lead to a similar N—N distance. Supposing that all CCC- and CSiC-bond angles are equal (tetrahedral angles), and... 

Among these compounds, transition metal alkyls are the most widespread. For simple metal alkyls, the M — R bond distance is typically 190 to 220 pm. This is approximately the sum of the covalent radii of carbon and metal, rc = 77 pm and rM 120pm [184h]. Simple alkyls are simple a-donors (Fig. 2.5). 

The Ge atom in 154 is pentacoordinated due to intramolecular N —Ge coordination and it has a distorted TBP arrangement at the germanium center, with three equatorial carbon atoms and axial chlorine and nitrogen. The axial bond lengths (Table 36) are significantly longer than the sum of the covalent radii for these elements (Table 1). 

Talfle LXI I. Comparison of Experimental Values of Interatomic Distances with the Sum of Covalent Radii for Bonds involving Carbon (A)... 

In this compound, too, the intemuclear distances indicate that bonding between the metal atoms is important The Al-Al distance is only 0.10 A more than the value calculated for a single bond by doubling the tetrahedral covalent radius, and 0.24 A less than the Al—Al distance in the metal The Al—Cb bonds on the other hand are 0.18 A longer than the Al—Cj bonds. The latter are equal to the Al—C single-bond value 1.96 A, calculated from the tetrahedral covalent radii of carbon and aluminum and the revised Schomaker-Stevenson mle. 

Revised Values of Double-Bond Covalent Radii.—This investigation has led to the value 1.34 A. for the carbon-carbon double-bond distance, 0.04 A. less than the value provided by the table of covalent radii.111 4 Five years ago, when this table was extended to multiple bonds, there were few reliable experimental data on which the selected values for double-bond and triple-bond radii could be based. The single-bond radii were obtained -from the study of a large number of interatomic distances found experimentally by crystal-structure and spectroscopic methods. The spectroscopic value of the triple-bond radius of nitrogen (in N2) was found to bear the ratio 0.79 to the single-bond radius, and this ratio was as-... 

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