Other Metal Compounds with Bridging Alkyl Groups

OTHER METAL COMPOUNDS WITH BRIDGING ALKYL GROUPS... 

An operational description is that one reactant (the more ionic compound with the more electropositive metal) transfers alkyl anions to the other. Thus the four methyl groups in Li2BeMe4 form a distorted tetrahedron around the beryllium, with longer distances to the lithium ions. However, this description is oversimplified. The low-temperature nuclear magnetic resonance (NMR) spectrum of Li3MgMe5 has three different methyl resonances, suggesting structure (14), related to the MeLi tetramer. Ate complexes with zinc and aluminum compounds also form. Electron-deficient bridge-bonded structures, exemplified by the X-ray structure of... 

Characteristic of most reactive RM compounds is their existence as two or more R M units closely associated with each other. The nature of these metal alkyl complexes has been extensively studied via X-ray crystal analysis by Rundle and co-workers, who showed that the a-carbon atom of the alkyl groups forms a bridge between metal atoms in different RM units. Thus, the dimer of trimethyialuminum may be viewed as... 

We have developed efficient syntheses of. /w-(hy(iroxy)dibenzo-16-crown-5 and jyw-(alkyl)(hydroxy)dibenzo-16-crown-5 compounds 17,18). These lariat ether alcohols, in which the alcohol function and a hydrogen atom or alkyl group are attached to the central carbon of the three-carbon bridge serve as platforms for attachment of various potential coordinating groups to provide a variety of other lariat ether compounds. For example, dibenzo-16-crown-5 lariat ethers with pendent amide 19), ester 20) and thioamide (27) groups have been prepared. To further probe the effect of structural variation within lariat ethers, studies of metal perchlorate transport across bulk chloroform membranes by dibenzo-16-crown-5 lariat ethers with oxyacetamide and oxythioacetamide side arms were undertaken. 

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