Synthesis and structural characterization of monomeric selenolato complexes of zinc, cadmium, and mercury

Abstract

The synthesis and characterization of homoleptic zinc(II), cadmium(II), and mercury(II) selenolates incorporating the intramolecularly chelating oxazoline ligand are described. The derivatives, M[Se(Ox)]₂ [M=Zn (1), Cd (2), Hg (3); Ox=2-(4,4-dimethyl-2-oxazolinyl)benzene], were prepared in good yield via the metathesis reactions of MCl₂ with a lithium areneselenolate, OxSe-Li⁺. The mercury complex 3 was also synthesized by treating the corresponding diselenide with elemental mercury. The complexes are quite stable and highly soluble in common nonpolar organic solvents. X-ray diffraction results show that the complexes are monomeric in the solid state. The geometry around the metal ion in all complexes is found to be distorted tetrahedral. The crystal structure of Zn[Se(Ox)]₂ (1) shows that the complex is "helically" chiral and enantiomerically pure. The spontaneous splitting of the racemates indicates the solubility differences between the racemates and pure enantiomers. ¹H, ¹³C, and ⁷⁷Se NMR measurements indicate that complex 1 retains its "helical" structure in solution. Crystal data (Mo Kα; 293(2) K) are as follows: 1, monoclinic space group P2₁, a=9.3900(12) Å, b=11.618(2) Å, c=10.8822(14) Å, β=98.245(8)°, Z=2; 2, orthorhombic space group Pbca, a=12.777(6) Å, b=17.841(10) Å, c=21.010(8) Å, Z=8; 3, monoclinic space group P2₁/c, a=9.087(2) Å, b=11.889(2) Å, c=22.456(4) Å, β=98.780(13)°, Z=4.