Monovalent complexes

Fig. 11 Schematic drawing of neutral and monovalent complexes based on the organometallic-dithiolene compounds...

For both classes of compounds, the chemistry of the group 13 trivalent and monovalent complexes proceeds similarly for Al, Ga, and In, and so these complexes will be treated together. Much of the chemistry of thallium compounds tends to be unique and will largely be handled separately. 

The rearrangement rate for the four-coordinate Cu(II) complex is smaller than for the monovalent complex. It is nevertheless several orders of magnitude larger than in related catenanes or rotaxanes with more encumbering ligands ... 

It is evident that monovalent complex ions cannot condense in this way both NOf and ClOjf would lose their charge and become unable to form complexes by condensation without change of their coordination number to... 

Fig. 10 Principle behind electrochemically induced molecular motion in a copper(l) complex pseudorotaxane. The stable, four-coordinate, monovalent complex is oxidized to an intermediate tetrahedral, divalent species. This compound undergoes a rearram gementto afford the stable, five-coordinate...

Fig. 17 Electrochemically triggered rearrangement of a [2]-catenate containing two different rings. The stable, 4-coordinate monovalent complex [top left, the black circle represents Cu (I)] is oxidized to an intermediate, tetrahedral, divalent species [top right, the white circle represents Cu (I I)]. This compound...

Reversing the process, reduction of the stable species 26 62+ affords 26 +, which rapidly rearranges to the stable monovalent complex 26(4)+. The intermediate 26(5 + has not been isolated nor spectroscopically characterized, but its formation was clearly evidenced by cyclic voltammetry, due to its analogy with 23 +. 

The exchange of monovalent complexes of zinc ions it can be excluded by thermodynamic calculations. At pH < 6, an insignificant portion (<0.1) of zinc ions is present as ZnOH+ complexes (Pourbaix 1966). Neither can other anionic complexes be present in the applied concentration ranges (Horne et al. 1957). 

Exhaustive electrolysis of the zinc(II) catenate at the first reduction wave plateau (-1.1 V) leads to the formation of a pink-red solution (2 iax = 530 mn, e 1000 cm ) of the corresponding monovalent complex. EPR measurements performed on a frozen solution of the electrochemically generated monovalent zinc catenate show the presence of a paramagnetic radical species (g = 2.00246, A/7 = 11.46 G). The reduced states Zn.S and Zn.5", containing formally monovalent and zerovalent zinc, respectively, are better described as zinc(II(-stabilized anion radicals. 

Figure 33. Principle of operation for inducing ring rotation in a nonsymmetrical [2]catenate. Horizontal arrows represent redox processes, vertical arrows represent rearrangements. Cu" is a solid circle, whereas Cu is an open circle. The stable four-coordinate monovalent complex Cu (4) (top left) is oxidized to the intermediate tetrahedral divalent species Cu"(4j (top right) which rearranges to the stable five-coordinate Cu (5) complex, bottom right. Upon reduction, the five-coordinated monovalent Cu (s) is formed (bottom left) which finally undergoes conformational changes to restore the starting Cu (4) (top left).

It is noteworthy that the redox couples of reactions 1-3 [Eq. (1)] are perfectly reversible provided the scan rate is sufficient (>100 mV s 1). The gliding motions, either for the divalent or the monovalent complex, are slow on the time scale of the voltammetry measurements (lines 2 and 4). 

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