Magnesium (II) poly(pyrazolyl)borate derivatives – Synthesis, spectral and structural studies

A series of magnesium complexes of general formula [Mg(Tpx)2] (Tpx = Tp, Tp∗, Tp∗Cl, pzTp) and [Mg(Tpx)X] (X = Cl, Tpx = TptBu or pz0Tpp-Tol; X = acetate, Tpx = TptBu) were synthesised from magnesium chloride or acetate and M(Tpx) (M = K, Na or Tl) in dichloromethane or alcoholic solution. These compounds are air-stable solids, sparingly soluble in most organic solvents; they have been characterized by elemental analysis, IR, 1H and 13C NMR spectra and, in selected cases, also by conductivity and molecular weight measurements. Single crystal X-ray diffraction studies of [Mg(Tp)2], [Mg(Tp*)2] and [Mg(Tp*Cl)2] show unsolvated neutral bis(tripod ligand)magnesium(II) molecules with six-coordinate magnesium atoms (〈Mg–N〉 2.167(6), 2.19(2), 2.205(4) Å).