Coordination Chemistry of Mercury-Containing Anticrowns. Complexation of Perfluoro‑o,o′‑biphenylenemercury with o‑Xylene and Acetonitrile and the First X‑ray Diffraction Evidence for Its Trimeric Structure

The paper reports the first X-ray diffraction data evidencing the cyclic trimeric structure of the earlier synthesized octafluoro-o,o′-biphenylenemercury (8), being of considerable interest as a potential anticrown. The conclusion on the trimeric (o,o′-C6F4C6F4Hg)3 structure of this mercuracycle is based on an X-ray structural analysis of its o-xylene and acetonitrile complexes {[(o,o′-C6F4C6F4Hg)3]­(o-Me2C6H4)2} (9) and {[(o,o′-C6F4C6F4Hg)3]­(MeCN)3} (10), which were obtained from 8 in an analytically pure state and fully characterized. Complex 9 contains two o-xylene species per one molecule of 8 and forms in the crystal infinite chains consisting of alternating mercuramacrocycle units and bridging o-xylene ligands. One more o-xylene molecule in each macrocyclic fragment of the chain serves as a terminal ligand. Both bridging and terminal molecules of o-xylene are coordinated in all cases with only one Hg site of the corresponding mercuracycle. The back transformation of complex 9 into 8 and o-xylene occurs on its heating in a vacuum at 100–120 °C for 2 h. In contrast to 9, complex 10, containing three acetonitrile ligands per one molecule of 8, has a discrete structure in the crystal. In this complex, two of three acetonitrile species are bonded to one and the same Hg center of 8, whereas the third MeCN species is coordinated with the other Hg atom of the mercuramacrocycle.