Octahedral complexes stability

Low-spin, octahedral complexes are formed by ligands such as bipy, phen and CN , and their stability is presumably enhanced by the symmetrical configuration. [Fe(bipy)3] + and [Fe(phen)3] + are stable, intensely red complexes, the latter being employed as the redox indicator, ferroin , due to the sharp colour change which occurs when strong oxidizing agents are added to it ... 

Thc Crystal l-ield Siabili2ation Energy (CFSl ) is the additional stability which accrues to an ion in a complex, as compared to the free ion, because its d-orbitals are split In an octahedral complex a l2 electron increases the stability by 2/5Ao and an Cf, electron decreases it by 3/5Ao- In a tetrahedral complex the orbital splitting is reversed and an e electron therefore increases the stability by 3/5At whereas a t2 electron decreases it by 2/5Ai. 

Since hydrofluoride synthesis is based on thermal treatment at relatively high temperatures, the possibility of obtaining certain fluorotantalates can be predicted according to thermal stability of the compounds. In the case of compounds whose crystal structure is made up of an octahedral complex of ions, the most important parameter is the anion-cation ratio. Therefore, it is very important to take in to account the ionic radius of the second cation in relation to the ionic radius of tantalum. Large cations, are not included in the... 

C20-0095. The d i and. y 2- orbitals have the same stability in an octahedral complex. However, in a square planar complex, the orbital is much less stable than the d orbital. Use orbital sketches to... 

As the trans effect theory indicates, there should be some relationship between lability of a ligand and its role as a labilizing group in another position in a complex. In an octahedral complex reacting via a dissociative mode of activation, the transition state has five strongly bound ligands. This state will be stabilized... 

An explanation of the direct 4s contribution to the charge density at the nucleus requires MO calculations. A simple MO diagram for octahedral complexes is shown in Fig. 4.4. The a-interaction of metal /-orbitals and symmetry-adapted ligand orbitals usually yields the major part to the stability of the bonds. According... 

Vahrenkamp and co-workers formed a number of chelate-stabilized ketone complexes with pyridylphenyl ketone. Octahedral complexes formed with a 2 1 ratio of ligand to zinc were formed with trifluoromethanesulfonate, chloride, and bromide anions. 1 1 reactions resulted in the formation of square pyramidal [ZnL2X]+ with X = Br, I, and a trigonal-bipyramidal dimer [L2Zn(NCS)2]2 with thiocyanate bridges.350... 

Many additional studies have since been made. A summary of the results for a number of octahedral complexes is given in Table 10.5. The predictions of ligand field theory are clearly borne out by the results, which show pronounced depopulation of the field-destabilized e g orbitals and increased population of the stabilized t2g(eg, ag) orbitals relative to the distribution in the high-spin spherical atom. 

Dr. Halpern This could be used in stabilizing, say an activated complex. The point about the hydrolysis observation is that this refers to the octahedral complex, whereas the explanations that have been offered for the effect of amide in the conjugate base mechanism are concerned, not with weakening of the binding, but with stabilizing a five-coordinated intermediate. I wondered if the role of the hydroxide in promoting water substitution might be of the same nature. 

Since the first report of a complex involving a direct metal-to-Ceo bond, (Ph3P)2 Pt( 7 -C6o)/ numerous studies have established that the fullerene Ceo acts as a moderately electronegative alkene in coordinating to electron-rich metal centers. In many cases the Ceo ligand is subject to relatively facile displacement when the complex is in solution however, the zerovalent, octahedral complexes M(CO)3(dppe)(Cgo) [M = Mo, W dppe = l,2-bis(diphenylphosphino)ethane] display outstanding stability even under severe conditions. The overall time needed to prepare these complexes from commercially available M(CO)g is dramatically reduced by adopting a biphasic procedure for the synthesis of the precursor M(CO)4(dppe), which was first described for the preparation of Mo(CO)4 (dppe). Here details are presented for the biphasic synthesis of W(CO)4(dppe) and for its use in the preparation of W(CO)3(dppe)(Cgo)-... 

Ligand-field theory predicted (10, 22) that tetrahedral nickel(II) complexes should be unstable with respect to octahedral ones, at least so long as the two extra ligands were available. This arises because, if one accepts the d-orbital center of gravity as an energy-zero (a point which should be raised more often), the crystal-field stabilization of an octahedral complex works out to be 0.84 A greater than that of a tetrahedral complex with... 

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