Methyl substituted benzene adducts of trimeric perfluoro-o-phenylene mercury
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abstract
Trimeric perfluoro-ortho-phenylene mercury (1) dissolves in substituted benzenes including toluene, ortho-xylene, meta-xylene, para-xylene and is sparingly soluble in mesitylene. The199Hg NMR resonance of 1 in toluene, ortho-xylene, meta-xylene, and para-xylene appears at 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 1toluene (2), 1ortho-xylene (3), 1meta-xylene (4), 1para-xylene (5) and 1mesitylene (6), respectively, as crystalline complexes. These adducts have been characterized by elemental analysis and X-ray crystallography. Thermogravimetric analyses indicate that 25 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 26, the resulting HgCaromatic distances are in the range 3.23.5 and are within the sum of the van der Waals radii. They reflect the presence of secondary polyhapto -interactions occurring between the electron-rich aromatic molecules and the acidic mercury centres. 2003 The Royal Society of Chemistry.
