Synthesis and structures of hypervalent organoantimony and organobismuth chlorides containing asymmetric C,E,C-chelating (E = O, S) ligands

Two asymmetric tridentate C,E,C-chelating ligand precursors, 1-Br-2-[(2′-BrC₆H₄CH₂E)CH ₂]C₁₀H₆ (E = O (1), E = S (2), were prepared in good yield. Lithiation of the two precursors was achieved by a reaction with n-BuLi, and was followed by treatment with SbCl₃ or BiCl₃ in a 1:1 molar ratio to give four air-stable hypervalent organoantimony and organobismuth chlorides with an asymmetric C,E,C-chelating ligand (E = O, S), i.e. (C₆H₄CH₂OCH₂C ₁₀H₆)SbCl (3), (C₆H₄CH ₂SCH₂C₁₀H₆)SbCl (4), (C ₆H₄CH₂OCH₂C₁₀H ₆)BiCl (5) and (C₆H₄CH₂SCH ₂C₁₀H₆)BiCl (6). These compounds were characterized by NMR spectroscopy, elemental analysis and melting point determination. X-ray structure analysis of compounds 3-6 revealed that the donor atoms (O, S) are strongly coordinated to the metal atoms (Sb, Bi). Compounds 3-6 exhibit chirality and crystallize as racemic mixtures.