Structure and UV spectroscopic properties of a novel dendritic oligosilane

The reaction of (R2MeSi)2MeSiLi (2) [R=SiMe3] with [ClMe2Si]2 yields the double-cored dendritic oligosilane [(RMe2Si)2MeSiSiMe2]2 (4). The structure of 4 was obtained from X-ray diffraction data, which verify a total of 16 silicon atoms in the molecule and a longest chain of 8 silicon atoms. 4 exhibits an absorption maximum in the near UV at 285 nm (ε=5.6×104), a wavelength that is significantly longer than that of the linear octasilane Si8Me18 and is the longest observed for structurally well-defined oligosilane dendrimers so far.