Amines Jahn-Teller distortion

A general approach for predicting Jahn-Teller distortions of copper(II) hexa-amines has recently been published, and it has the potential to be applied to donor atoms other than nitrogen, metal centers other than copper(II), and various types of coordination polyhedra11641. The method is based on a harmonic first-order model11651 where the Jahn-Teller stabilization energy is the result of the Qg distortion mode (Fig. 11.1, Eqs. 11.3, 11.4). 

The polyaminocarboxylate-derivative of cyclam, TETA, forms Cu-complexes with coordination number 6 with involvement of four amino groups and two pendant carboxylates (Moi et al. 1987). Surprisingly, Jahn-Teller distortion involves two amines and not the carboxylates as expected. Again, the Copper-complex coupled to an antibody loses less than 1% of its metal per day when incubated in human serum. 

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]. 

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