Coordination of silicon tetrafluoride with alicyclic ethers and dimethyl ether

Tensimetric titrations at −78° of silicon tetrafluoride with ethylene oxide, trimethylene oxide, tetrahydrofuran, tetrahydropyran, and dimethyl ether prove the formation of only 1:2 complexes, SiF4•2-(ether). All are unstable at 25° and either dissociate completely, as do SiF4•2(CH2)4O, SiF4•2(CH2)5O, and SiF4•2(CH3)2O, or decompose into SiF4 and a polymethylene oxide polymer, as do SiF4•2(CH2)2O and SiF4•2(CH2)3O. Silicon tetrafluoride does not coordinate with 1,4-dioxane in the range −94 to 25° and less than 1 atm pressure. Condensed phase heats of dissociation of SiF4•2(ether) complexes follow the order (CH2)3O > (CH2)4O > (CH2)5O ≥ (CH2)2O > (CH3)2O, which suggests that this is the relative order of basicities towards SiF4.