Atoms charge stability

The benzyhc complex has been synthesized at low temperatures and may owe its stabiUty to possible multihapto coordination, Tj —Tj, of the benzyl ligand. The methyl complex is stable even up to room temperature. Six of the methyl groups are hydrogen-bonded to the Li atom to stabilize this highly charged species. This compound is very reactive with and CO. However, there is no concrete stmctural data for the final products of such reactions. 

Compare atomic charges and electrostatic potential maps of the two carboeations. In which is the positive charge more delocalized For each carbocation, draw whatever resonance contributors are needed to account for all of your observations. Which carbocation is better stabilized by resonance ... 

The fact that the equilibrium for aminopyridine 1-oxides is displaced further in favor of the amino form than is the equilibrium for aminopyridines is in accord with the mesomerism of these compounds. The stabilization of the amino forms (e.g., 241) by structures of type 240 is more effective than the corresponding stabilization in the pyridine series since the negative charge is associated with the oxygen atom. The stabilization of the imino form (e.g., 242) by structures of type 243 is less than in the pyridine series because of the adverse inductive effect of the oxygen atom. ... 

When nitrogen is in an " inductive position of an adjoining ring, the charge stabilization could be greater for a nitrogen atom at the center (5-position in 56) of the pentadienoid transition state than at the 7-position (57), even though the distances from the reaction site are... 

The three structures of type 4 are unstable for two reasons the presence of electric charges of the same sign on adjacent atoms, and the use by the nitrogen atom of only three orbitals. The contribution of these structures to the normal state of the molecule is accordingly small, and we may take it to be zero. Also, structures of type 3, with a double bond and the transfer of the positive charge to a fluorine atom, are stabilized by the formation of an additional covalent bond with use of the fourth orbital and may accordingly make a greater contribution to the normal state moreover, there is an extra factor 2 for the six structures of type 3 over the three of type 1. 

When there is no conjugated substituent able to stabilize the positive charge development, the bromine atom is involved in the charge stabilization and the... 

The most important factor for determining charge stability is to ask what atom the charge is on. For example, consider the following two structures ... 

In accord with the resonance structure drawn, there is little B=B bonding in this diborane(4) derivative and the B—B distance is found to be 1.859 A,68 which is considerably longer than even the normal expected value of 1.7 A for a boron-boron single bond.67 This is consistent with the normal repulsion of negative charges on adjacent atoms not stabilized by 7r-bonding. 

The term metalla-/3-diketonate refers to an anionic diacyl complex, such as L M(RCO)(R CO) , in which the two acyl ligands occupy adjacent coordination sites of the metal atom. Resonance stabilization of the negative charge by 7r-delocalization onto the two acyl ligands gives Lewis structures 1 and 2. The two acyl ligands acquire an acyl/carbene... 

Table 3.29. The NBO descriptors of XYZ triatomic anions (see Table 3.28), showing natural atomic charges (Q), percentage polarization of oxy and ayz NBOs toward terminal atoms, second-order nz— oxy and nx->OYZ stabilizations (A/s(2)), and occupancies of valence antibonds (oxy and ayz ) and extra-valent Rydberg orbitals (ry ) parenthesized values refer to Lewis structure of lower accuracy...

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