Methyl substituted benzene adducts of trimeric perfluoro-o-phenylene mercury

Trimeric perfluoro-ortho-phenylene mercury (1) dissolves in substituted benzenes including toluene, ortho-xylene, meta-xylene, paraxylene and is sparingly soluble in mesitylene. The 199Hg NMR resonance of 1 in toluene, ortho-xylene, meta-xylene, and para-xylene appears at (delta)-1051.8, -1053.5, -1051.4 and -1059.1 ppm, respectively. These resonances are slightly upfield from the resonance observed for 1 in CH2Cl2(-1045.2 ppm) and possibly indicates the solvation of the mercury centres by molecules of arenes. Slow evaporation of solutions of 1 in toluene, ortho-xylene, meta-xylene, para-xylene and mesitylene affords 1·toluene (2), 1·ortho-xylene (3), 1·meta-xylene (4), 1·para-xylene (5) and 1·mesitylene (6), respectively, as crystalline complexes. These adducts have been characterized by elemental analysis and X-ray crystallography. Thermogravimetric analyses indicate that 2-5 begin to lose the coordinated arene at a temperature below 50 °C; however, in the case of 6 loss begins around 91 °C. The structures of 2, 4 and 5 reveals the existence of binary stacks in which the aromatic core of the benzenes approaches the mercury centres of 1. In the case of 3 and 6, the aromatic molecule appears preferentially bound to one of the two proximal molecules of 1. Hence, 3 and 6 are best described as discrete 1:1 complexes. In 2-6, the resulting Hg...Caromatic distances are in the range 3.2-3.5 (angstrom) and are within the sum of the van der Waals radii. They reflect the presence of secondary polyhapto (pi)-interactions occurring between the electronrich aromatic molecules and the acidic mercury centres.