Tetrakis 2,4,6-trimethylphenyl disilene Tetramesityldisilene

Submitted by ROBIN P. TAN, GREGORY R. GILLETTE, HOWARD B. YOKELSON, and ROBERT WEST  

As silicon is the element most similar to carbon, compounds containing multiple bonds to Si have long been sought. Tetramesityldisilene, the first stable compound containing a silicon-silicon double bond, was initially prepared in 1981 by ultraviolet irradiation of 2,2-dimesityl-l,l,l,3,3,3-hexamethyltrisilane. Photolysis of the trisilane produces dimesitylsilylene, which dimerizes to form the disilene. 

The synthesis detailed here is a variation of the original photolytic method, requiring the synthesis of the trisilane as a precursor. The trisilane is prepared by coupling dichlorodimesitylsilane with chlorotrimethylsilane, using lithium metal in tetrahydrofuran (THF). The synthesis of dichlorodimesitylsilane has been described previously. It is also available commercially.t 

Similar photolysis of trisilanes may be used to generate other stable disilenes. Stable disilenes can also be synthesized by photoinduced fragmentation of cyclotrisilanes, and, in some cases, by dehalogenation of dihalo-diorganosilanes.  

All reactions are performed under an atmosphere of argon or dry nitrogen in oven-dried glassware (120°C). Because of the moisture-sensitive nature of 

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