Coordination chemistry of anticrowns: Complexation of cyclic trimeric perfluoro-o-phenylenemercury with nitro compounds

Cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 (1) is capable of reacting with nitromethane to give complex {[(o-C6F4Hg)3](CH3NO2)} (2) containing one molecule of the nitro compound per one macrocycle molecule. In this complex, the nitromethane ligand is bound to 1 by its both oxygen atoms, one of which is simultaneously coordinated to all three Hg centres of the macrocycle while the other interacts with a single Hg centre. The complex of similar composition, {[(o-C6F4Hg)3](C6H5NO2)} (3), is produced in the interaction of 1 with nitrobenzene. In this complex too, the both oxygen atoms of the nitro group are involved in the bonding to the macrocycle. A distinctive feature of 3 is that here one oxygen atom of the coordinated nitro derivative is bound by only two Hg centres of 1 whereas the other interacts again with a single Hg site. The reaction of 1 with 5-nitroacenaphthene affords a 1:1 complex, {[(o-C6F4Hg)3](C12H9NO2)} (4), having a polydecker sandwich structure in the crystal. Unlike in 3, the aromatic rings of the nitroarene units in 4 are disposed virtually in parallel to the macrocycles. The nitro compound in 4 behaves again as a bidentate ligand, forming three Hg–O bonds with one of the adjacent macrocycles and a single Hg–O bond with another molecule of 1. The complex is characterized also by shortened Hg–C contacts between the Hg centres of 1 and the carbon atoms of the nitroarene moiety as well as shortened C–C contacts between the carbon atoms of the nitroarene and the macrocycle. In the interaction of 1 with 1-nitropyrene, complexes of two compositions, viz. {[(o-C6F4Hg)3](C16H9NO2)} (5) and {[(o-C6F4Hg)3](C16H9NO2)3} (6) are formed. An X-ray diffraction study of 6 has shown that in this adduct two of three coordinated molecules of the nitro compound are located on one side of the metallacycle plane while the third nitroarene molecule is disposed on its other side. The aromatic rings of all three nitropyrene ligands in 6 are practically parallel to the mean plane of the macrocycle. In contrast to 2–4, each molecule of the nitroarene in 6 is bonded to 1 by a single oxygen atom which is coordinated only to one Hg centre. In the case of one of the nitropyrene ligands that forms much longer Hg–O bond with 1 than two others, an additional contribution to the bonding is made by shortened Hg–C contacts between the macrocycle and the carbon atoms of the aromatic pyrene core and also by shortened C–C contacts between the carbon atoms of the coordinated nitroarene and 1. The synthesized adducts are the first examples of complexes of an anticrown with nitro compounds.

The ability of the mercury anticrown (o-C6F4Hg)3 (1) to bind nitro compounds is reported. In the case of nitromethane, nitrobenzene and 5-nitroacenaphthene, 1:1 complexes are formed, differing, however, in their structures. With 1-nitropyrene, 1:1 and 3:1 complexes were isolated. The synthesized adducts are the first examples of complexes of nitro compounds with an anticrown.Figure optionsDownload as PowerPoint slide