Electron imbalance

Normally, an increase in effective electronegativity of a particular group attached to the tin atom is expected to increase the imbalance in the population of the p orbitals and so give a shift to higher frequencies but any use of the tin d orbitals to form % bonds would tend to offset this effect. If the overall number of electronegative substituents is increased, the effective electronegativity of the tin atom itself will also increase and so the p electron imbalance in each bond may decrease and the tin nucleus may experience increased shielding. 

Carbon surfaces hold a charge density that arises fiom electron imbalances due to the incomplete coordination of their outermost atoms. In order to minimize the electrical difference between the surface and the bulk of the solid, the charge held is balanced by the redistribution of surrounding ions, resulting in electrostatic interactions between the ions/molecules in solution and the carbon surface. The result is diat the attracted ions approach the carbon sur ce, as predicted tty Coulomb s law, creating a drop in the electric potential which is confined to a limited region in solution (termed die outer Helmholtz Plane) and fonn the so-called electrical double layer (EDL). 

The proposed structure of the complex Is of Interest In that the electron deficient rings A and B lie over the electron rich rings C and D and this electron Imbalance could be an Important factor In determining the geometry of these aggregates. Note also that a layered structure of alternate rings Is entirely feasible on this basis and this Is In accord with the observed data. 

Table 3.12 Bond distances M-C (d, A), and electron imbalance 8 in sandwich complexes...

Hall and Ykman have studied the reactions of a series of electron-deficient tri-substituted ethylenes (33) with a series of electron-rich olefins (34). Rates of reaction increase sharply with increasing electronic imbalance between the reaction partners. The kinetically favoured products are cyclobutanes, but these isomerize or undergo cycloreversion in polar solvents or on heating, behaviour which is consistent with the intermediacy of zwitterionic intermediates. Olefin metathesis is observed when the electronic imbalance is extreme. 

A measure of the p electron imbalance, with the P2 state of Xe atom corresponding to a unit hole in the 5p shell. Approximate, assuming the bonding involves transfer to the ligands of 5p electrons only, leaving hp holes in the 5p shell of Xe. 

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