Perfluorinated Diindacycles

The reaction of 1,2-bis(halomercurio)tetrafluorobenzene (halide = chloride (3) or bromide (4)) with the corresponding indium(I) halide in THF results in spontaneous ring closure and formation of the tetrakis(THF) adducts of 9,10-dichloro-9,10-dihydro-9,10-diindaoctafluoroanthracene (5) and 9,10-dibromo-9,10-dihydro-9,10-diindaoctafluoroanthracene (6), respectively. Diindacycle 6 can also be prepared by reaction of indium(I) bromide with trimeric perfluoro-o-phenylenemercury in refluxing toluene, followed by treatment with THF. Upon addition of pyridine, the ligated THF molecules of 6 are readily displaced and 9,10-dibromo-9,10-dihydro-9,10-diindaoctafluoroanthracene tetrakis(pyridine) (7) is obtained. Compounds 5−7 have been characterized by ¹H, ¹³C, and ¹⁹F NMR spectroscopy, MSCI, and elemental analysis, and their molecular structure has been determined by single-crystal X-ray analysis. All compounds crystallize in monoclinic space groups. Two modifications of compound 6 have been analyzed. 5:  space group P2₁/c with a = 9.686(1) Å, b = 11.071(1) Å, c = 15.725(2) Å, β = 105.55(1)°, V = 1624.5(3) ų, and Z = 2. 6:  space group P2₁/c with a = 9.636(1) Å, b = 11.129(1) Å, c = 16.029(2) Å, β = 104.40(1)°, V = 1664.9(3) ų, and Z = 2; space group P2₁/n with a = 10.258(1) Å, b = 13.926(1) Å, c = 11.892(2) Å, β = 97.86(1)°, V = 1682.8(2) ų, Z = 2. 7:  space group P2₁/c with a = 17.632(2) Å, b = 15.010(1) Å, c = 14.562(1) Å, β = 101.72(1)°, V = 3773.6(6) ų, and Z = 4. The perfluorination of the phenylene rings in 5−7 has a consequent effect on the Lewis acidity of the indium centers which is reflected by the relatively short O−In and N−In dative bond distances.