Organoaluminum structure

The structures of substantial numbers of simple organoaluminum species have been reported during the past few years. The initial structure determined was that of trimethylaluminum (IV) (68). Subsequently, the structure has been redetermined in the solid state (116) and attempts have even been made to determine the location of the hydrogen atoms to provide details concerning the bonding present within this molecule (54). 

The structures of several other symmetrical organoaluminum compounds, which have important implications with regard to electron-deficient bonding, have been determined from X-ray data. The first of these (VI) shows the structure of tricyclopropylaluminum dimer (84, 99). In this compound, the A1—C—A1 bridge is symmetrical and the cyclopropyl rings are oriented so that the p orbital on the bridging carbon atom may interact with the appropriate vacant orbitals on the metal atoms. This interaction appears to increase the stability of the bridge bond as indicated from variable-temperature NMR studies. The... 

Structural Parameters for a Variety of Bridged Organoaluminum Derivatives... 

Organoaluminum azides R2A1(N3) and RA1(N3)2 are known the former type adopts a cyclic structure, [Me2Al(N3)] where n — 2 or 3, based on four-coordinate aluminum with bridging... 

Yasuda,H., Araki.T., Tani,H. Structure and chemical behavior of an organoaluminum [R2A10CR NPh]2. A stereospedfic catalyst for polymerization of acetaldehyde. J. Organomatal. Chem. in press. 

Diene polymerization via lanthanide propanolate-based catalytic systems was first reported by U. Pedretti et al. [162], Several types of binary and ternary initiator systems have been developed since the late 1970s (see Table 7), including zz- and zsopropanolalc ligands [162], homo- and heteroleptic lanthanide species [163-165], and different types of organoaluminum cocatalysts [162,166-168]. Despite such extensive studies, structural evidence of the formation of alkylated rare-earth metal centers remained scarce. 

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