Trigonal bipyramidal complexes configuration

It should be noted that these spectra bear the expected similarity to those of trigonal bipyramidal complexes of the d configuration, for example TiBr3(NMe3)2. 

Type III. In this category of reaction, metal valence electrons are moved into energetically preferred spatial configurations with respect to the nonreacting ligands. An example is the transformation of the trigonal bipyramid complex 45 to 46. This process is similar to Type II transformations in that... 

Calculation has shown that the most stable configuration of the initial catalyst is not the octahedral complex having a vacant site, as the Cossee mechanism proposes, but rather, a trigonal-bipyramidal complex which is 1.43 eV lower in energy. This complex has an unpaired electron strongly localized in the highest stable orbital d i), which interacts with the titanium-alkyl bond. 

These conclusions are generally consistent with those derived from extended Hiickel calculations [27-29]. In their calculations on trigonal bipyramidal complexes, Rossi and Hoffmann [28] noted that the axial bonds are stronger than the equatorial bonds when the electron configuration is d for the central transition metal. Checking the experimental data (see Table 1 of Ref. [19]) for d trigonal bipyramidal structures, we cannot find much evidence for such a site preference effect. 

From the energy point of view, the solvated complex [Cu(H20)5] " undergoes frequent transformations between square pyramidal and trigonal bipyramidal (TBP) configurations by a Berry twists mechanism (Scheme 3). 

In the context of the Marcus formulation, the lowering of the activation barrier in an inner-sphere process could arise from the reduction of the work term wp as a result of the strong interaction in the ionic products, e.g., [RitSn+ IrCU3 ] and [RitSn+TCNE ]. The electrostatic potential in such an ion pair is attractive and may cause the tetraalkyltin to achieve a quasi five-coordinate configuration in the precursor complex, reminiscent of a variety of trigonal bipyramidal structures already well-known for tin(IV) derivatives, i.e.,... 

Distorted trigonal bipyramidal, with R = n-Bu. 229, 230 NH- -Cl hydrogen bonds are formed, as attested by IR spectra and some of the foreshortened N—Hal distances. Other similar structures are known, such as R = Ph, which also yields an aW-trans complex with two molecules of l-methyl-2(3H)-imidazolinethione, that has octahedral configuration. 

The corresponding [FeI(PP3)(C=C-Ph)] complex has been isolated and characterized. As shown in Figure 74, it maintains the trigonal bipyramidal geometry of the Fe(II) precursor and its magnetic moment indicates a low spin d7 configuration (e//4e/3 one unpaired electron ... 

---