where F1, Q and Z are all as previously defined and M is an alkali or alkaline earth metal is reacted with a bis (halohydrocarbyl) disiloxane of formula ##STR20## where D and R1 are as previously defined and X is Cl, Br or I at ambient pressure, at a temperature of from ambient (20??? C.) to 200??? C. in the presence of a dipolar aprotic liquid.