Novel Oxonium Halogenochalcogenates Stabilized by Crown Ethers: [H3O(Dibromo-benzo-18-crown-6)](2)[Se3B10] and [H5O2(Bis-dibromo-dibenzo-24-crown-8](2)[Se3Br8]

摘要

Two novel complex oxonium bromoselenates(II, IV) and -(II) are reported containing [H3O](+) and [H5O2](+) cations coordinated by crown ether ligands. [H3O(dibromo-benzo-18-crown-6)](2)[Se3Br10] (1) and [H5O2-(bis-dibromo-dibenzo-24-crown-8](2)[Se3Br8] (2) were prepared as dark red crystals from dichloromethane or acetonitrile Solutions of selenium tetrabromide, the corresponding unsubstituted crown ethers, and aqueous hydrogen bromide. The products were characterized by their crystal Structures and by vibrational spectra. 1 is triclinic, space group P (1) over bar (Nr. 2) with a = 8.609(2) angstrom, b 13.391(3) angstrom, c = 13.928(3) angstrom, alpha = 64.60(2)degrees, beta = 76.18(2)degrees, gamma = 87.78(2)degrees, V = 1404.7(5) angstrom(3), Z = 1. 2 is also triclinic, space group P (1) over bar with a = 10.499(2) angstrom, b = 13.033(3) angstrom, alpha = 14.756(3) angstrom, alpha = 113.77(3)degrees, beta = 98.17(3)degrees gamma = 93.55(3)degrees. V = 1813.2(7) angstrom(3), Z = 1. In the reaction mixture complex redox reactions take place, resulting in (partial) reduction of selenium and bromination of the crown ether molecules. In 1 the centrosymmetric trinuclear [Se3Br10](2-) consists of a central (SeBr6)-Br-IV octahedron sharing trans edges with two square planar (SeBr4)-Br-II groups. The novel [Se3Br8](2-) in 2 is composed of three planar trans-edge sharing (SeBr4)-Br-II squares in a linear arrangement. The internal structure of the oxonium-crown ether complexes is largely determined by the steric restrictions imposed by the aromatic rings in the crown ether molecules, as compared to complexes with more flexible unsubstituted crown ether ligands.