Ferrocene bis crown ethers

Studies on the Schiff base linked ferrocene bis-crown ether compound [6] have shown that it is not well-behaved electrochemically. 

We have recently demonstrated (Beer et al., 1995b,c) that it is possible electrochemically to detect simultaneously the presence of two different cations bound in the redox-active ferrocene bis-crown ether receptor [15] as shown in Fig. 10. 

We have also prepared the Schiff base and sulfur-linked ferrocene bis-crown ether ligands (65) (27) and (28) (Scheme 12). Preliminary coordination studies have shown both to be K + selective however, (27) is not electrochemically well behaved. Unexpectedly, addition of K + to electrochemical solutions of (28) results in a cathodic shift of the ferrocene redox couple, which may be attributable to conformational steric effects involving the sulfur heteroatom lone pairs of electrons. 

Amido-linked ferrocene bis-crown ethers (e.g., 55) are obvious analogues of the ferrocenophanes and among the earliest examples of macrocyclic derivatives of ferrocene [77—81]. 

Bis[copper(U) tris-pyrazolyl borane] dioxygen complex, 42 107-108, 110 Bis crown ethers, see Ferrocene, crown and bis crown ethers... 

Ferrocene Crown and Bis Crown Ethers Designed to Bind Group IA, IIA Metal Cations... 

Reaction of [l,r-ferrocenediyl6/s(methylene)]bi s[pyridinium] salt with diaza-12-crown-4 afforded the ferrocene crown ether l,l r,r -6(. s(ferrocenediyl)b/s[4,10-Ws(methylene)-1,7-dioxa-4,10-diazacyclododecane [95IC3964],... 

Fig. 8. Ferrocene bis amido aza crown ether 1 2 ligand alkali metal cation complexes.

Restricted C—N bond rotation is also a feature of metallocene-crown-ether complexes.In the complex (13) C—N rotation moves the amide carbonyl through a transition state in which the carbonyl rc-bond is orthogonal to the ground-state planar -bonding framework of the Cp-amide system. New ferrocene and ruthenocene bis(aza-crown ethers) of type (14) (n = 1, 2) exhibit rotation about the N—CO bond at rates which are cation (Na" or Li" ) dependent. The stoichiometry of the complexes are also cation dependent.Crown-ether dithiocarbamates exhibit restricted S2C—N bond rotation. In one case an energy barrier of 65.3 + 0.5 kJ mol was calculated, but this was significantly reduced to 54.5 0.5 kJ mol when the compound was studied in the presence of two equivalents of NaBPh4. This was attributed to the interaction between the Na" ions and the crown-ether... 

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