Probing the Lewis acidity of heavier pnictogen trichlorides

Lewis acidity of SbCl3 and BiCl3 has been investigated in the solid as well as in solution state. Two beta-ketoimine ligands, [O=C(Me)]CH[C(Me)NHAr] (L1, Ar=2,6-diisopropylphenyl) and [(CH2)(2){N(H)C(Me)CHC(Me)=O}(2)] (L2) are used to prepare the complexes [(L1)(THF)SbCl3](2) (1), [(L1)(THF)BiCl3](2) (2), [L2SbCl(3)](2) (3) and [(L2)(3)(BiCl3)(2)] (4), which are characterized by multinuclear NMR spectroscopy, elemental analysis and single-crystal X-ray diffraction experiments. Solid-state structural analysis of 1-4 and solution studies on SbCl3 and BiCl3 using the Gutmann-Beckett method reveal the higher Lewis acidity of BiCl3 compared to SbCl3.