Abstract
Reaction of 1,3-dilithio-1,3-bis(trimethylsilyl)allene and ClMe[sub 2]SiSiMe[sub 2[minus]]Cl in THF affords in combined 57% yield an ca. 1:1 mixture of meso and dl diastereomers. One of these diastereomers could be purified by fractional crystallization, thus allowing subtraction for the spectral features of the others. Assignment of structure could not be accomplished by NMR as chiral shift reagents were ineffective, but the meso structure was established for the selectively crystallized isomer by X-ray diffraction and the molecular structure is shown. The allene unit is bent only slightly from linearity to 178.6[degrees] but is twisted to produce a dihedral angle of 80.6[degrees] as defined as plane Si(1)C(1)C(2)vs Si(4)C(3)C(2). However, a dihedral angle of 86.1[degrees] is obtained from plane Si(1)C(1)Si(2)vsSi(3)C(3)Si(4), and comparison of plane Si(2)C(1)C(2) and Si(3)C(3)C(2) yields an apparently normal 89.4[degrees]. 14 refs., 3 figs., 1 tab.
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