Nickel Jahn-Teller effect

Jahn-Teller effects), nickel(II) complexes have been used in the molecular mechanics design. They too are labile enough. Some of the systems discussed in the literature are presented in Table 7.2. 

Binary transition metal complexes have been the subject of a wide range of studies regarding their structure and spectroscopy for many years beginning with Mond et al. [4] who first reported Ni(CO)4 whilst investigating the Action of Carbon Monoxide on Nickel in 1890. A wide range of spectroscopic methods and techniques has subsequently been utilised, including X-ray and electron diffraction, IR, and UV/Vis spectroscopy. In almost all cases the Jahn-Teller effect has been invoked to explain certain spectroscopic features. Due to a wide breadth of smd-ies reported in the literature, this review will not be comprehensive. Instead it is... 

Octahedral High-spin Cobalt(II) and Tetrahedral Nickel(II). The results on octahedral cobalt(II) and tetrahedral nickel(II) compounds will be considered jointly, since identical expressions apply to the calculation of the transition energies, 10 Dq, and B. The Jahn-Teller effect (76) in the ground state, a T g, of octahedral ions is expected to be weak and may be disregarded for the present purpose. On the other hand, a strong Jahn-Teller effect is predicted for tetrahedral d ion ground states (57). 

Jahn-Teller distortions 309 ff Japanese separators 264, 267 Joule effect, heat losses 13 jump frequency, solid electrolytes 532 Jungner nickel cadmium batteries 22... 

Liehr has shown (142) that the orbital degeneracy of the ground state in a tetrahedral nickel(II) complex may be lifted by spin-orbit coupling. This means that these complexes may not be liable to Jahn-Teller distortion as has been thought for some time. Such coupling would also have the effect of splitting all transitions into several components, the exact number... 

Figure 3 depicts a schematic of how one can arrive at different meso-ciystal structures. Consideration of the coordination environment of the metal ions is crucial for predicting the nature of the resulting meso-ciystal. For example, a nanocomposite mesociystal may be obtained of phase-separated CuO and ZnO (Fig. 3b). This is due to the differing coordination environments of the copper ions (Cu in Jahn-Teller distorted octahedra in CuO) and the zinc ions (Zn in a tetrahedral environment in ZnO). On the other hand, a solid solution of Zno 2Nio sO is formed when zinc and nickel nitrates are employed as precursors, since the coordination environments are similar. One strength of this synthetic approach is the effective charge transfer which can occur in...

Reactions in Water.—A preliminary report has indicated that the rate of water exchange in the five-co-ordinate Co complex of (7) is particularly low for this metal (4.2 X 10 s at 25 °C) the activation parameters are given as A/f = 36.5 1.4 kJ mol and AS = — 34 4 JK mol. A preliminary application of conductometric pulse radiolysis to the dissociation of Co -amine chlorides has yielded results consistent with those obtained by other methods. The very small effect exerted by nickel(ii)-bound pyridine on the lability of the remaining water molecules has already been mentioned. An interesting preliminary report has indicated that the substitution reactions of Cu complexes are relatively slow in the absence of Jahn-Teller distortions [as, for example, in the trigonal-bipyramidal complex with (8) see Table 7]. 

---