Synthese und Kristallstruktur von Iodmethyltriphenylphosphonium-iodid (C6H5)3PCH2I+I- / Synthesis and Crystal Structure of Iodomethyltriphenylphosphonium Iodide (C6H5)3PCH2I+I-

Iodomethyltriphenylphosphonium iodide, (C₆H₅)₃PCH₂I⁺I-, has been prepared by the reaction of (C₆H₅)₃P with CH₂I₂ in dichloromethane forming colourless needle like crystals. The crystal and molecular structures have been determined by an X-ray structure analysis. The crystals are orthorhombic, space group Pca2₁, Z = 8; a = 1478,8(3) pm, b = 1249,3(3) pm, c = 2053,2(3) pm. R = 0.050 for 3219 observed reflections with I ≥ 2 σ(Ι). In the solid state the title compound exists as two discrete monomeric units, (C₆H₅)₃PCH₂I⁺I-. In both symmetry independent units the I-I distances are surprisingly short with 346,5(1) pm and 356,3(1) pm. For the title compound the results of AM 1, PM 3, and MNDO calculations are in good agreement with corresponding values determined by the X-ray analysis.