Concave π-prismand hydrocarbon [2.2.2]cyclophanes and their crystalline Ag-triflate complexes

New small concave hydrocarbon cyclophanes were prepared via the well-known HD-2SO₂-method. The cyclophanes obtained are isomers of the very well-known 2.2.2]p,p,p-cyclophane, C₂₄H₂₄, a π-prismand efficiently complexing Ag⁺-ion. X-ray crystal structure determinations showed the bis-sulfide 7 (1,10-dithia3.3.2]m,p,p-cyclophane) to be helically chiral and that the conformation of the parent hydrocarbon cyclophane 13 (2.2.2]m,p,p-cyclophane) does not change dramatically upon complexation with the Ag⁺-ion. The 16- and 17-membered 2.2.2]m,m,p- and 2.2.2]m,p,p-cyclophane ( 15 and 16 ) also act as π-prismands and form surprisingly similar crystalline 1:1 Ag-triflate complexes (π-prismates) as the well-known 18-membered p,p,p-isomer proved by the X-ray structure analysis.