Abstract 1,1,1,5,5,5-Hexamethyltrisiloxane (I) was prepared by reaction of (Me3SiO)2Mg or of Me3SiOH with dichlorosilane. Its selective chlorination to give mostly Me3SiOSiHClOSiMe3 and only a small amount of Me3SiOSiCl2OSiMe3 was effected by its PdCl2-catalyzed reaction with CCl4. Photolysis of compound I gave H(Me3SiO)2SiSi(OSiMe3)2H in 30% yield, as well as polymer.