Inverse crowns

This section is limited to complexes which have a group 1 metal in conjunction with another, different main group metal, but also includes Cu and Cd since they exhibit properties akin to their main group analogs. It is also limited mainly to those complexes in which the metals find themselves attached to different atoms and there is a particular emphasis on compounds with alkali metal-carbon bonds of various types, except where the evolution of inverse crown complexes is discussed. There are many more heterobimetallic-heteroatom complexes (e.g., mixed metal amides), but these lie outside the scope of this current review though references may be found to them in the references for the complexes described herein. 

In a deliberate attempt to trap the carbanion/amide intermediates formed en route to the homoamido inverse crown complexes, [ (TMP)(/z-Bu)(/x-TMP)NaMg(TMEDA) ] 432 (Figure 38) was isolated and characterized.440 This complex spans the superbase and inverse crown structural modalities. 

Figure 46 The structure of the inverse crown derivative, [Na4Mg4(NPr 2)8Fe(C5H3)2] 95.

Figure 47 The structure of a inverse crown with multiple deprotonated ferrocenes 96.

Figure 48 The structure of the heterotrimetallic inverse crown 97 (for clarity, Bu groups attached to nitrogen atoms are not shown).

Tab. 3.6-1. Compositions of inverse crown ethers [(M1 )2(M2)2(amide)4(core)]. ...

Fig. 3.6-2. Inorganic cluster core of super inverse crown ethers of general formula [ NaMg(amide)0(THF) 6], where amide = TMP (2,2,6,6-tetramethylpiperidinide) or DPA (diisopropyl-amide).

The ether designation is dropped here because these inverse crowns do not contain any oxygen-based anions. 

FIGURE 3. Example of an inverse crown containing a 1,4-phenylene dianion... 

FIGURE 16. Part of the polymeric chain of inverse crown ether structure 15... 

This compound represents an example of an inverse crown ether stmcture (Lewis acidic host-Lewis basic guest macrocyclic heterometallic alkoxides or amides/ . 

FIGURE 26. Molecular geometry of inverse crown architecture 40 in the solid state... 

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