Highly Fluorinated Aryl-Substituted Tris(indazolyl)borate Thallium Complexes: Diverse Regiochemistry at the B–N Bond

The synthesis and characterization (mainly by ¹⁹F NMR and X-ray diffraction) of highly fluorinated aryl-4,5,6,7-tetrafluoroindazoles and their corresponding thallium hydrotris­(indazolyl)­borate complexes are reported [aryl = phenyl, pentafluorophenyl, 3,5-dimethylphenyl, 3,5-bis­(trifluoromethyl)­phenyl]. Thanks to N–H···N hydrogen bonds, the indazoles crystallize as dimers that pack differently depending on the nature of the aryl group. The thallium hydrotris­(indazolyl)­borate complexes Tl­[Fn-Tp^4Bo,3aryl] resulting from the reaction of aryl-4,5,6,7-tetrafluoroindazoles [aryl = phenyl, 3,5-dimethylphenyl, 3,5-bis­(trifluoromethyl)­phenyl] with thallium borohydride adopt overall <i>C</i>_3<i>v</i> symmetry with the indazolyl groups bound to boron via their N-1 nitrogen in a conventional manner. When the perfluorinated pentaphenyl-4,5,6,7-tetrafluoroindazole is reacted with thallium borohydride, a single regioisomer of <i>C</i>_<i>s</i> symmetry having one indazolyl ring bound to boron via its N-2 nitrogen, TlHB­(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol-1-yl)₂(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol-2-yl) Tl­[F27-Tp^(4Bo,3C6F5)*], is obtained for the first time. Surprisingly, the perfluorinated dihydrobis­(indazolyl)­borate complex Tl­[F₁₈-Bp^3Bo,3C6F5], an intermediate on the way to the hydrotris­(indazolyl)­borate complex, has <i>C</i>_<i>s</i> symmetry with two indazolyl rings bound to boron via N-2. The distortion of the coordination sphere around Tl and the arrangement of the complexes in the crystal are discussed

Highly Fluorinated Aryl-Substituted Tris(indazolyl)borate Thallium Complexes: Diverse Regiochemistry at the B–N Bond

The synthesis and characterization (mainly by ¹⁹F NMR and X-ray diffraction) of highly fluorinated aryl-4,5,6,7-tetrafluoroindazoles and their corresponding thallium hydrotris­(indazolyl)­borate complexes are reported [aryl = phenyl, pentafluorophenyl, 3,5-dimethylphenyl, 3,5-bis­(trifluoromethyl)­phenyl]. Thanks to N–H···N hydrogen bonds, the indazoles crystallize as dimers that pack differently depending on the nature of the aryl group. The thallium hydrotris­(indazolyl)­borate complexes Tl­[Fn-Tp^4Bo,3aryl] resulting from the reaction of aryl-4,5,6,7-tetrafluoroindazoles [aryl = phenyl, 3,5-dimethylphenyl, 3,5-bis­(trifluoromethyl)­phenyl] with thallium borohydride adopt overall <i>C</i>_3<i>v</i> symmetry with the indazolyl groups bound to boron via their N-1 nitrogen in a conventional manner. When the perfluorinated pentaphenyl-4,5,6,7-tetrafluoroindazole is reacted with thallium borohydride, a single regioisomer of <i>C</i>_<i>s</i> symmetry having one indazolyl ring bound to boron via its N-2 nitrogen, TlHB­(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol-1-yl)₂(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol-2-yl) Tl­[F27-Tp^(4Bo,3C6F5)*], is obtained for the first time. Surprisingly, the perfluorinated dihydrobis­(indazolyl)­borate complex Tl­[F₁₈-Bp^3Bo,3C6F5], an intermediate on the way to the hydrotris­(indazolyl)­borate complex, has <i>C</i>_<i>s</i> symmetry with two indazolyl rings bound to boron via N-2. The distortion of the coordination sphere around Tl and the arrangement of the complexes in the crystal are discussed