Inner-orbital complex

For more information see Colloidal Chemistry Inner Orbital Complex... 

Crystal field designation for an inner orbital complex contains electrons paired t2g orbitals before eg orbitals are occupied in octahedral complexes. 

Inner-orbital complexes are formed by ions of the transition metals, regardless of the nature of the ligands, provided ( —l)d orbitals can be made available... 

But 6-co-ordinate inner-orbital complexes of Co and NF+ are unlikely since they would require the promotion of one or two electrons to the 4d level. 

Copper(I) and zinc do not form inner-orbital complexes the promotion of four electrons would be required in each case ... 

The inner-orbital complexes show a sharp decrease in lability at the stage where no d orbital is left vacant. A pronounced difference in bond type cannot be expected in the following ... 

In the early use of VB theory, complexes in which the electronic configuration of the metal ion was the same as that of the free gaseous atom were called ionic complexes, while those in which the electrons had been paired up as far as possible were called covalent complexes. Later, first row metal complexes in which ligand electrons entered 3[Pg.557]

According to VBT, octahedral complexes may be either outer-orbital complexes involving sp d hybridization or inner-orbital complexes resulting from d sp hybridization. In both the cases, eg orbitals are involved in the hybridization. 

The central met ll atom or ion may use inner (n-l)d orbitals or outer nd orbitals for hybridization. On this basis, the complexes may be classified as follows (I) Inner orbital complexes The complexes which use inner d-orbitals, i.e., (n - 1) d orbiteds of the central metal atom or ion for bond formation are called as inner orbital complexes. These complexes formed by strong ligands i.e., CN, NO2, CO, NH3 etc. In these complexes the impaired electrons of the central metal atom or ion are forced to pair up by strong ligands against Hund s rule. These complexes are, therefore, either diamagnetic or contain lesser number of unpaired electrons. They are also called low spin or spin paired complexes. These complexes... 

Since inner 3d orbitals are used for bond formation, it is called inner orbital complex. Due to less number of unpaired electrons, it is a low spin complex and is diamagnetic as it does not contain an unpaired electron. 

Taube s classification designates complexes as labile if they react completely at room temperatures within the time of mixing 0.1 If solutions, and as inert if under these conditions the rate of reaction can be followed by conventional kinetic techniques. For six-coordinated complexes on the basis of the valence bond theory it is possible to classify labile systems as being either outer-orbital complexes ([CoFe] , [A1(C204)3] , [Fe(H20)6] +, etc.) or inner-orbital complexes having at least one vacant d orbital (CTiFe] , CV(H20)6] ", [Sc(H20)6] , etc.). It follows then that only inner-orbital complexes containing no vacant d orbitals are inert, e.g., [Co(NH3)6] +, [Cr(H20), +, [Fe(CN) ] -, etc. 

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