Tetrahedral complexes valence bond theory

Valence bond theory describes the bonding in complexes in terms of two-electron, coordinate covalent bonds resulting from the overlap of filled ligand orbitals with vacant metal hybrid orbitals that point in the direction of the ligands sp (linear), sp3 (tetrahedral), dsp2 (square planar), and d2sp3 or sp3d2 (octahedral). 

According to valence bond theory, what set of orbitals is used by a Period 4 metal ion in forming (a) a square planar complex (b) a tetrahedral complex ... 

Pauling s valence bond theory is likewise of only limited value in its application to transition metal complexes. In the VBT, the ligand electrons are accommodated in hybrid orbitals localized on the central metal. The orbitals of interest for transition metals are the nd, n -f 1), n + l)p, and n + )d. An octahedral configuration arises from d sp hybridization of the metal orbitals, while dsp hybridization gives the square planar structure and sp hybridization results in a tetrahedral geometry. 

With some ligands, such as Cl-, Ni(ll) forms tour-coordinate complexes that are paramagnetic and tetrahedral. For these cases. V ) theory assumes the d orbital occupation of Lhe complex to be the same as that of the free ion, which eliminates the possibility that valence-level d orbitals can accept electron pairs from the ligands-Hybrid orbitals of either the tp or At/5 type (the latter involving -level d orbitals) or a combination of the two provide the proper symmetry for the o bonds as well as... 

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