Bonding range

One member of this class, the 8-cyano derivative 2, has been described.414 X-ray crystallography shows that the scvcn-mcmbcrcd ring adopts a chair conformation with the S S bonds ranging in lengths from 205 to 206 pm. 

The only structurally characterized In—Sb adduct is (Me3SiCH2)3 In—Sb(Tms)3 19 [38], featuring an In—Sb bond distance of 300.8(1) pm. Due to the lack of other structurally characterized In—Sb adducts, no structural comparisons can be made. The In—Sb bond length found in 19 is supposed to be at the lower end of the In—Sb dative bond range since the covalent radius of In (r ov 143 pm) is about 17 pm larger than those of the lighter elements Al and Ga. Therefore, In—Sb dative bonds are expected to... 

Cluster 1 is a conventional [4Fe-4S] cubane cluster bound near the N-terminus of the molecule as shown in Fig. 13. Within the cluster the Fe-S bonds range from 2.26 to 2.39 A. The cluster is linked to the protein by four cysteine residues with Fe-S distances ranging from 2.21 to 2.35 A, but the distribution of the cysteine residues along the polypeptide chain contrasts markedly with that found, for example, in the ferredoxins as indicated in Section II,B,4 [also see, for example, 41) and references therein]. In the Fepr protein all four cysteine residues (Cys 3, 6, 15, and 21) originate from the N-terminus of the molecule, and the fold of the polypeptide chain in this region is such that it wraps itself tightly around the cluster, yet keeps it near the surface of the molecule. In such a position the cluster is ideally placed to participate in one-electron transfer reactions with other molecules. 

Dispersion forces, dipole Interactions, and hydrogen bonds all are significantly weaker than covalent Intramolecular bonds. For example, the average C—C bond energy Is 345 kJ/mol, whereas dispersion forces are just 0.1 to 5 kJ/mol for small alkanes such as propane. Dipolar Interactions between polar molecules such as ace-tone range between 5 and 20 kJ/mol, and hydrogen bonds range between 5 and 50 kJ/mol. 

Polar bonds range from bonds between atoms that have large but slightly less than integral charges and are therefore close to the ionic limit to pure covalent bonds between... 

An Sn2 reaction requires an approach by the nucleophile to a distance within bonding range of the carbon atom bearing the leaving group. 

Diethylzinc forms a colorless monoadduct with l,4-diazabicyclo[2,2,2]octane (dabco) 34 and an orange-colored bis-adduct with acridine.79 The mono-dabco adduct, Figure 14, crystallizes in the form of infinite zigzag chains, in which each diethylzinc moiety bridges two dabco units. The coordination environment about zinc is distorted tetrahedral, with Zn-C and Zn-N bonds ranging from 1.93(3) to 2.10(2) A and from 2.24(2) to 2.37(2) A, respectively. 

The coordination geometry about zinc is perfectly planar with an angle sum of 360°. The Zn-C bonds range from 2.032(2) to 2.058(2) A. 

The solid-state structure of 166 shows that the pentamethylcyclopentadienyl ligands are symmetrically bound to the zinc atoms in a pentahapto fashion, with isometric Zn-C bonds, ranging from 2.27 to 2.30 A. 

The series E(NSO)2 (39a-c E=S, Se, Te) exhibit planar, acyclic structures with a cis arrangement about the two S=N bonds. The central E-N bonds are essentially single bonds. The S=N bond distances fall in the double bond range with a significant shortening of this bond along the series. 

Germanium provides two examples of the tetracyclooctagermane L, with R = f-Bu and X = Cl or Br Ge—Ge bonds range from 244-254 pm, with those involving GeX the shortest. 

In this chapter we illustrated how the CASSCF/CASPT2 method can be used to explore the nature of such chemical bonds. Classic cases are the Re-Re multiple bond in Re2Cl, and the Cr-Cr bond ranging from the quadruply bonded Cr(II)-Cr(II) moiety to the formal hextuple bond between two neutral chromium atoms. The bonding between the 3d5 electrons is weak and should be considered as an intermediate between two pairs of antiferromagnetically... 

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