Outer-orbital complex

Oudeman law physchem The law that the molecular rotations of the various salts of an acid or base tend toward an identical limiting value as the concentration of the solution is reduced to zero. od-a-man, I6 ) outer orbital complex phys chem A metal coordination compound in which the d orbital used in forming the coordinate bond is at the same energy level as the s and p orbitals. aud-or 6rb-od-3l kam.pleks) overall stability constant analychem Reaction equilibrium constant for the reaction... 

The electron arrangement in an outer orbital complex such as [Mn(ox)3]3 can be shown as follows ... 

Some complexes utilize inner d orbitals of the central ion, while others are outer-orbital complexes ... 

Crystal field designation for an outer orbital complex all t2g and eg orbitals are singly occupied before any pairing occurs. 

Henry Taube Itmer and outer orbital complexes... 

FIGURE 10-2 Inner and Outer Orbital Complexes. In each case, ligand electrons fill the d sp bonding orbitals. The remaining orbitals contain the electrons from the metal. 

For outer-orbital 6-co-ordinate complexes, lability is associated with a charge of under four on the central ion, and inertness with one of four or over. These outer-orbital complexes probably undergo unimolecular dissociation and the ligand is easier to remove when the central charge is low. It is characteristic of the metals which give outer-orbital, 6-co-ordinate complexes readily, that they should also form 4-co-ordinate complexes. 

Care should be taken to distinguish these terms from the expressions inner orbital and outer orbital complex ions which have been introduced recently for an entirely different purpose 45). 

In six-coordinated systems, the hybrid orbitals involve the s, p py p, and atomic orbitals. The resulting six sp (f or cf sp hybrid orbitals point toward corners of an octahedron. For [CoFe] the d orbitals used have the same principal energy level as the s and p orbitals. A complex of the nsnp ruf type is called an outer-orbital complex because it uses outer d... 

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. 

Since outer 4d orbitals are used for bond formation, it is called outer orbital complex. Due to the presence of large number of impaired electrons, it is high spin complex. It is highly paramagnetic due to e presence of four unpEiired electrons. 

Tables 2.4.3 and 2.4.5 show that, for d , d and d complexes, crystal field stabilization energies (AE ) are negative or zero, which means that their reactions are fast regardless of the mechanism. In fact, these complexes are labile. On the other hand, d octahedral complexes as well as d, d and d complexes have positive AE, which indicates slow reactions. Indeed, complexes of this type are inert. In addition, d and d and d complexes ( outer-orbital complexes, i.e., complexes of a weak crystal field) are labile, as expected. Their AE are negative or zero (E is lowered) and therefore the reactions are fast regardless of the mechanism).

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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