Six-ring complexes

If, while formulating the theory, the valency angles are considered, and the alkoxy group is marked as a chain, the relationship to the six-ring complexes (4) formulated in the reaction of Meerwein-Pondorf-Verley and Claisen-Tishchenko is at once clear. 

Figure 5. Hypothetical intermediary term II as six-ring complex.

This method utilizes aluminum as a reducing agent and aluminum chloride as both a reactant and a catalyst, and it is a very convenient reaction for the preparation of such aromatic, six-ring complexes. It is not necessary to conduct the reaction in a sealed tube if a trace of mesitylene is employed as a starting agent. The complex cation bisben-zenechromium(I) also is formed by the reaction of chro-mium(III) chloride with phenylmagnesium bromide at low temperatures. 

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