Organometallic compounds solvent coordination effects

One of the more important recent developments in organometallic aluminum chemistry has been the formation and isolation of low-coordinate compounds, and, in particular, cations. These were first prepared in reactions of various aluminum reagents with crown ethers to form the inclusion compounds known as liquid clathrates. 71,72 Most of the evidence supports the presence of ion pairs as the basis of the solvent inclusion effect. Indeed, the compound [AlMe2-18-crown-6]+[AlMe2Cl2] was isolated from one such system (the cation is shown in Figure 6(a)).73 This was the first time the Me2Al+ unit had been structurally characterized. 

In our early studies we observed with R. Jones and others, some significant solvent effects on coordination or complex formation as they influenced the reactivities of some organometallic compounds. They had been known for some time, and appeared rather striking when examined in connection with Michler s ketone and the color test. From our study it appeared that the order of decrease in relative reactivity and increase in tendency to form coordinate compounds with ketones was PhLi, PhMgBr, PhjGa. 

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