Unusual host−guest complexes with dienophiles have been synthesized by the interaction of cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 (3) with p-benzoquinone (BQ) and maleic anhydride (MA). In the case of BQ, the resulting complex {[(o-C6F4Hg)3]2(BQ)} (4) contains one molecule of a dienophile per two molecules of the macrocycle. According to X-ray diffraction data, it has a sandwich structure wherein a dienophilic guest is located between the mutually parallel planes of two macrocyclic hosts and is bonded to each of these through a symmetrical coordination of its carbonyl oxygen atoms by all Hg centers of the neighboring macrocycle. The reaction of 3 with MA results in the formation of a sandwich complex, {[(o-C6F4Hg)3]2(MA)2} (5), containing two dienophilic species per two macrocycles. In this unique sandwich, both molecules of the dienophile are arranged between the mutually parallel planes of the macrocycles and are coordinated to their Hg centers by the oxygen atoms of the carbonyl groups. Each molecule of MA in complex 5 is bound by three Hg−O bonds with one of the macrocyclic hosts and by only one Hg−O bond with the other molecule of 3.