N bond order

Properties and Reactions. The stmcture of (aLkyl)imiQoboranes RB=NR is characterized by ahnear C—B—N—C geometry and a B—N bond order approaching three. Amino iminoboranes can be described usiag three resonance stmctures ... 

The sign of PTS with respect to various pairs of positions in conjugated polyenes in their ground state was investigated 143>. The result is indicated in Fig. 7.32. The n bond order is always positive in the cases where... 

The n( [) bond order was calculated according to the empirical logarithmic function (1) proposed by Pauling and adapted by Burgi 25... 

Monomeric iminoboranes exhibit a B-N bond order higher than unity due to p - p bonding between nitrogen and three-coordinate boron. This event results in an allene-type structure as shown in (I) exhibiting its antisymmetric stretching vibration around 1800 cm-1. This should have a predominant i>(CN) character, whereas in the symmetric mode of lower wavenumber the B-N charac-... 

Aromaticity indices based on a statistical evaluation of peripheral bond orders have been derived for five-ring heterocycles a value of 50 for 1,3,4-oxadiazole compares with values of 43 and 66 for furan and thiophene respectively <85T1409>. Somewhat in contrast, O—C, C—N, and N—N bond orders of 1.3124, 1.9062, and 1.3348 (MMX, EXE calculation) for 1,3,4-oxadiazole led to the conclusion that the molecule was not aromatic <91H(32)2023>. 

Structure type Ring system Substituents Orbital energies Net charges n-bond orders ... 

Acetyl peroxynitrate (18) and perfluoroacetyl peroxynitrate (19), two important atmospheric oxidation products of hydrocarbons (formation of 18) or chlorofluorocarbon replacements, such as CF3CH3 (formation of 19), preferentially adopt a gauche conformation (C—O—O—N = 84.7° for 18 and 85.8° for 19 electron diffraction). The two peroxides are characterized by comparatively short 0—0 bonds on one side and long 0°—N connectivities (Table 5) on the other. The observed O —N distances may be explained on the basis of an no ct od-n orbital overlap. This type of interaction lowers the 0°—N bond order and could explain the low bond dissociation energies of this connectivity in peroxides 18 and 19 (118 4 klmol for both compounds). It should be noted that this interpretation does not reflect a possible r-type interaction between a lone pair at 0° and virtual orbitals of the nitro group and therefore requires future investigation. 

Amides and related compounds have been thoroughly investigated as ligands for alkali metals. Studies in solution have been made using various physicochemical techniques these, and MO calculations, show that the interaction of amides with M+ is via the carbonyl function.56,57 This leads to a delocalization of the amide N electron pair and so it is possible to follow the decrease in C—O, and the increase in C—N, bond orders using IR spectroscopy. X-Ray crystal structures of amide complexes have shown both types of complexation interaction to be present (Table 2). 

If one considers the metal to be Tav, the Ta=N bond then implies a combination of ligand to metal o and n donation from a formal N2 ligand, with unit N—N bond order. The experimental N—N bond lengths suggest bond orders between 1 and 2, consistent with donation of electrons from the nr 2p orbitals of N2 into the empty d orbitals of Tav.320 This description also accounts for the eclipsed conformation of the equatorial ligands in (19), although the staggered one should be the more favored sterically.309... 

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