Transitional metal complex ion

A CT transition which is very similar to the -> MMCT transition has been observed by Vogler et al. [55] for complexes [M(2,2 -bipyridyl)X3] with X = Cl, Br, I and M = Sb, Bi. These authors report MLCT transitions involving the promotion of an electron from the lone pair to the n orbital of the bipyridyl ligand. For example, for M = Sb and X = Br they observe an orange color for the complex due to an absorption band with a maximum at 435 nm. In the complexes considered by us the transition is to an antibonding n orbital (with pronounced d character) on the filled-shell transition-metal complex ion. 

KEY TERMS transition metal complex ion copolymers cross-linked polymers... 

H. A. Kuska and M. T. Rogers, in Radical Ions (E. T. Kaiser and L. Kevan, eds.), Wiley, New York, 1968. Electron Spin Resonance of First Row Transition Metal Complex Ions. ... 

Table 5. Analysis of the nuclear quadrupole coupling resonance frequencies of transition metal complex ions of the type MX%...

The nuclear quadrupolar resonances observed for transition metal halides which form molecular crystals are very similar to those observed for the transition metal complex ions, and can also be divided into the same two classes (Table 9). One class again having coupling constants of the order expected from electronegativity considerations, the other having anomalously low ones. 

The interlayer regions of clay minerals also have cation-exchange capability and can be modified by organotransition metal compounds. Montmorillonite is typical of these materials and is readily intercalated with transition metal complex ions. The layered stractme of montmorillonite is shown in Figure 3. 

Although Pmssian Blue, synthesized in 1704, was the first officially recognized metal coordination complex to be made, discovery of this group of transition metal complex ions is often credited to Taessert, who in 1798 prepared the first known cobalt ammonia salts. His work inspired a revolution in inorganic chemistry. At the turn of the nineteenth century, amidst the flourishing developments of organic chemistry, the striking colors... 

Rate constant data for several homonuclear electron transfer reactions involving transition metal complex ions in water are summarized in table 7.1. The striking feature of the results is that the rate constants vary over a very wide range from a low 2x 10 s to a high of 4 x lO M s. Since these... 

Table 7.1 Kinetic Data for Homonuclear Electron Transfer Reactions Involving Transition Metal Complex Ions in Water at 25°C [5] ...

McClure DS (1960) Electronic structure of transition metal complex ions. Radiat Res Suppl 2 218-242... 

Notice that a transition metal complex ion is written in square brackets and the overall charge on the ion is written outside the brackets. In this example, the copper ion carries two positive charges and the water molecules are neutral, so the overall charge on the ion is 2-I-. The number of atoms directly attached to the central metal atom (in this example, six) is called the coordination number. 

When association does produce spectral change the form such change takes is variable. Cases are known of band shift, or of change in extinction coefficient, or perhaps only one band in the total spectrum is influenced. This latter is the case with transition metal complexes, ion association usually resulting in the appearance of a new band. With most complexes such ion-pair bands occur at shorter wavelengths than the transitions,... 

Inorganic chemists use ligand field theory, an approximate quantum-mechanical method, to predict and explain the properties of transition-metal complex ions. 

Valence-bond theory has been used to describe the electronic structure of transition-metal complex ions, with such concepts as d sp hybridization of the metal orbitals. However, the simple VB treatment of complex ions is not fully satisfactory and has been replaced by ligand-field theory, which is MO theory applied to species whose atoms have d (or /) electrons (see Murrell, Kettle, and Tedder, Chapter 13 Offenhartz, Chapter 9). 

A certain transition-metal complex ion absorbs at 630 nm. Which color is this ion most likely to be blue, yellow, green, or orange ... 

The nature of the barriers to intramolecular rearrangement and of the transition states has been considered for a wide variety of trigonal-bi-pyramidal molecules, including phosphorus(v) compounds such as PFs, PF2CI3, other neutral molecules such as SbMes and NbClg, and even transition-metal complex ions such as CuClg " and Ni(CN)6 ". ... 

A solution containing a certain transition-metal complex ion has the absorption spectrum shown here. 

Kuska, H. A. Rogers, M. T. Electron Spin Resonance of Transition Metal Complex Ions. In Coordination Chemistry, ACS Symposium Series. No. 168, Martell, A. E., Ed. Van Nostrand New York, 1971, 186-263. 

FIGURE 1 A schematic absorption spectrum of a transition metal complex ion in the UV-VIS region. The central ion bands correspond to d d transitions the ligand bands correspond to charge transfer transitions and/or to intraligand transitions. 

Describing the bonding in a complex ion Given a transition-metal complex ion, describe the bonding types (high-spin and low-spin, if both exist), using crystal field theory. (EXAMPLES 233,23.6)... 

The formation of dative bonds between a pair of reacting chemical species is the basis of a theory of acidity known as Lewis theory (Chapter 18). Dative bonds are also involved in the formation of transition metal complex ions (Chapter 13). Dative bond formation is often part of organic reaction mechanisms (Chapter 20). Aqueous solutions of acids contain the oxonium ion, H30, a datively bonded species (Chapter 8). 

Figure 13.32 Generalized explanation for formation of transition metal complex ions the transition metal ion can accept lone pairs (ligands) into suitably orientated empty hybridized orbitals... 

Planck s equation and the wave equation (Chapter 2) can be used to determine an approxirrmte value for the energy gap of a transition metal complex ion from the frequency or wavelength of the light most strongly absorbed by the ions of a complex ion. (This is an approximate value because the absorption spectrum is broad - it is not a single sharp peak.)... 

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