Takeo Araki

Structure and chemical behavior of an organoaluminum compound [Rb2AlOCR′NPh]2, a stereospecific catalyst for polymerization of acetaldehyde

A series of organoaluminum compounds [R2AlOCR′NPh]2, which are the reaction products between trialkylaluminum compounds and secondary acid amides and are excellent catalysts for stereospecific polymerizations of aldehydes, were isolated in the crystalline state. Chemical behavior of such compounds toward Lewis acids and bases were interpreted in terms of the structures of [Me2AlOCPhNPh]2 and its trimethylamine oxide complex Me3NO·AlMe2OCPhNPh which were determined by X-ray structure analyses. Reaction products of primary and tertiary acid amides with trialkylaluminum compounds were also studied.

Monomer-catalyst complexes in the stereospecific polymerization of aliphatic aldehyde. The structure and chemical behavior of the aldehyde complex of [R2AlOCR′NPh]2

The reaction between some aliphatic aldehydes (acetaldehyde, propionaldehyde and butyraldehyde) and the typical stereospecific polymerization catalyst R2AlOCR′NPh has been studied in an attempt to elucidate the initiation mechanism of the polymerization reaction. The monomer-catalyst (1/1) complexes obtained from these aldehydes and R2AlOCR′NPh possess excellent catalytic activity towards the stereospecific polymerization. The structure of the complex in solution has been determined by NMR and IR spectra and compared with the structure determined by X-ray structure analysis. The presence of pentacoordinate aluminum in the complex has been demonstrated, for the first time, by X-ray studies. n nThe structure of the aromatic monoaldehyde complex has also been studied and shown to be identical with that of the aliphatic aldehyde complex mentioned above. The chemical behavior of these aldehyde complexes towards Lewis bases and Lewis acids has also been studied. The aldehyde moiety of the R2AlOCR′NPh - MeCHO complex is liberated by the action of a strong Lewis base such as trimethylamine oxide and hexamethylphosphoramide, and is easily exchanged for another kind of aldehyde. The trimethylaluminum complex, Me2AlOCPhNPh · MeCHO · AlMe3, which only leads to the formation of amorphous polyacetaldehyde in contrast to Me2AlOCPhNPh · MeCHO, has been isolated and its structure determined by IR, NMR and X-ray studies in order to establish the relationship between its structure and its chemical behavior.