Structural Diversity of Organoantimony(III) and Organobismuth(III) Dihalides Containing O,C,O-Chelating Ligands

Eight organoantimony and organobismuth dihalides, containing two types of O,C,O-chelating (so-called pincer) ligands, 2,6-(ROCH₂)C₆H₃^- (R = Me, L¹; R = ^tBu, L²; L¹SbCl₂ (1), L²SbCl₂ (2), L¹SbI₂ (3), L²SbI₂ (4), L¹BiCl₂ (5), L²BiCl₂ (6), L¹BiI₂ (7), L²BiI₂ (8)) were prepared and characterized with the help of elemental analysis, electrospray ionization mass spectrometry, ¹H and ¹³C NMR spectroscopy, and X-ray diffraction techniques. Except for 5, which exists as a centrosymmetric dimer, all studied compounds are monomeric in the solid state and the coordination polyhedra of the central atoms are distorted square-pyramidal. Both oxygen donor atoms are coordinated to the central metal through moderately strong or strong intramolecular interactions (range of Sb−O distances 2.279(2)−2.6912(14) Å and Bi−O distances 2.379(3)−2.460(4) Å), both in cis fashion for 1 and 2 (angles O−Sb−O 116.65(5)° and 116.73(4)°) and trans fashion for 3, 4, and 6−8 (range of angles O−M−O; M = Sb or Bi, 142.26(12)−148.28(8)°). In noncoordinating solvents (CDCl₃, toluene-d₈) 1−8 display structures similar to those found in the solid state based on variable-temperature ¹H NMR measurements.