It was found that compound 1 crystallizes from thf–n-hexane solution with one thf molecule very loosely co-ordinated to calcium. (The poor quality of the crystals did not allow struc- ture refinement.) This indicates that the calcium atom in 1, although co-ordinated to eight fluorine atoms, is susceptible to additional co-ordination. In summary, compounds 1 and 2 are the first CaF2 inclusion compounds of fluoro analogues of crown ethers. The great difference in reactivity of bulk and in situ prepared CaF2 is demonstrated. The easy accessability of reactive CaF2 using the metathesis reaction of CaCl2 and trimethyltin fluoride in the presence of an organometallic compound opens up an interest- ing new field of chemistry. Moreover, this type of reaction is far superior to that using metals for the reduction of organo- metallic fluorides. The resulting compounds reported in this paper are diamagnetic instead of paramagnetic (as obtained using metals) and have allowed the elucidation of their struc- tures in solution using 19F NMR investigations.