Hybrid overlap

Each carbon atom is bonded to 4 other carbon atoms to form a tetrahedral shape in diamond. The bonds are formed by sp3-sp3 hybrid overlap. 

In graphite, a different form of carbon, atoms are bonded to each other in such a way that a hexagonal structure is formed in a plane. Each carbon atom is bonded to three other carbon atoms with an angle of 120° between the bonds. The bonding involves sp2 - sp2 hybrid overlap and this gives rise to layers. 

Two explanations were originally put forward to account for the asymmetry of sulphonyl carbanions. In the first [146] it was assumed that the carbanion is sp3 hybridized and pyramidal, for example, as shown in (XI) and (XII) and that the rate of pyramidal inversion was slower than the rate of protonation. This would explain why isotope exchange occurs more rapidly than loss of optical activity. An alternative explanation has been suggested in which the carbanion is assumed to be planar and sp2 hybridized. Overlap between the p-orbital with its pair of electrons and sulphur d-orbitals may be involved. A symmetric structure like (XIV) will not explain the results but an asymmetric structure (XIIII) in which asymmetry results from restricted rotation about the carbon—sulphur bond has been proposed [148]. Further, the kinetic results require that de-deuteration or protonation must occur preferentially from one side of... 

The same is true in (FeCl4) , although the positions of d and d orbitals are reversed and, in admitting covalency, the appropriate hybrids would be 4s 4p (tetrahedral). Such systems are often described as spin-free, outer orbital or high spin. In potassium hexacyanoferrate(III), however, [Fe(CN)g] occurs, and the moment (2.5 fjt indicates only one free spin evidently this is the strong-field case (Fig. 77(c)). The 3d orbitals are thus made available for bonding, and d sp hybrids overlap with, and partly accept, the carbon lone pairs of the CN groups, to produce six covalent bonds. Such systems are called spin-paired, inner orbital, or low spin complexes. 

The cation 28 consists of a hnearly coordinated sp-hybiidized metal nucleus (d nuclei hke Ag ) with strong imine N—Ag bonds, caused by substantial hybrid overlap with an imine-N lone pair, resulting in a short Ag-N distance of 2.16 A (av). The interaction of an empty perpendicular p orbital of Ag with the lone pairs of the thiophene S-group is extremely weak ( dipole-cation attraction ), with the Ag-S distance = 3.02 A. The N—Ag—N angles are 174.6 (av). The S donor atoms are directed towards the silver nucleus. The H, F NMR experiments and H- Ag decoupling experiment indicated that the Ag complexes are prone to intermolecular exchange processes (at 298 K) which become slow at low temperature (<255 K), whereas the intramolecular exchange processes are not ehminated even at 130 K. This can be corroborated by... 

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