Synthesis, spectroscopic, and X-ray diffraction structural studies of tin(IV) derivatives with tris(pyrazol-1-yl)methanes

The reaction of RSnCl3 (R = Me, Ph, or Bu-n) and SnX4 accepters (X = Cl, Br, or I) with equimolar amounts of tris(pyrazol-1-yl)methane ligands L (L = HC(pz)(3), HC(4-Mepz)(3), HC(3,5-Me(2)pz)(3), HC(3,4,5-Me(3)pz)(3), or HC(3-Mepz)(2)(5-Mepz) yields ionic 1:1 [{LSnRCl2}(+)][{SnRCl4}(-)] or [{LSnX3}(+)][{SnX5}(-)] and 2:1 [{LSnRCl2}(+)](2)[{SnRCl5}(2-)] or [{LSnX3)(+)](2)[{SnX6}(2-)] complexes, depending strongly on the number and position of the Me groups on the azole ring of the neutral ligand. These complexes, stable in air, have been characterized in the solid state (LR, MS-FAB) as well as in solution (H-1- and Sn-119-NMR, conductivity, and molecular weight determinations). The crystal and molecular structure of [{HC(4-Me(2)pz)(3)(SnBuCl2)-Bu-n}(+)](2)[{(SnBuCl5)-Bu-n}(2-)], [{HC(3,5-Me(2)pz)(3)SnMeCl2}(+)]-[{MeSnCl4}(-)], and [{HC(3,4,5-Me(3)pz)(3)SnBr3}(+)][{SnBr5}(-)] was determined by X-ray crystallography. The structures of the cations are very similar, the Sn atom being in a strongly distorted octahedral environment with the Sn-N bonds in the range 2.22-2.33 Angstrom whereas in the anions the Sn atoms are five-coordinate (trigonal-bipyramidal) in [MeSnCl4](-) and [SnBr5](-) and six-coordinate (octahedral) in [(SnBuCl5)-Bu-n](2-).