Acetylenkomplexe von Rhenium(+ VI). Die Kristallstrukturen von [ReCl4(n-C3H7 – C= C – n-C3H7)(POCl3)] und ReCl4(THF)2 / Alkyne Complexes of Rhenium(+VI). The Crystal Structures of [ReCl4(n-C3H7 – C= C – n-C3H7)(POCl3)] and ReCl4(THF)2

Abstract

The results of the magnetic susceptibility measurements of the previously reported rhenium alkyne complexes [ReCl4(PhC≡CPh)]2.2 CH2Cl2 and [ReCl4(PhC=CPh)(CH3CN)] in the temperature range of 4.2-293 K suggest d1-configurations, corresponding with oxidation state +VI for the rhenium atoms. The new alkyne complex [ReCl4(n-C3H7–C=C–n-C3H7)(POCl3)] has been prepared by the reaction of ReCl5·OPCl3 with n-C3H7-C≡C–n-C3H7 in CCl4 solution, forming dark red single crystals, which were characterized by IR spectroscopy as well as by a crystal structure determination with X-ray methods (space group P2,/c, Z = 4, 3235 observed unique reflexions, R = 0.026; lattice dimensions at –70 °C: a = 805.6(2), b = 1000.6(4), c = 2188.8(6) pm, β = 79.59(2)°). [ReCl4(n-C3H7-C=C–n-C3H7)(POCl3)] has a molecular structure with the alkyne ligand bonded side-on (bond lengths Re-C 198.4 and 198.2(5) pm). The oxygen atom of the solvating POCl3 molecule is coordinated in trans position to the ReC2 unit of the alkyne ligand (bond length Re—O = 223.7(3) pm). In THF solutions the alkyne complexes of this type undergo a slow reaction forming ReCl4(THF)2, which was also characterized by IR spectroscopy and a crystal structure determination (space group P212121, Z = 4, 2243 observed unique reflexions, R = 0.053; lattice dimensions at –70 °C: a = 773.0(14), b = 1267.1(6), c = 1398.6(7) pm). In ReCl4(THF)2 the THF molecules coordinate in cis-position (bond lengths Re–O 208 and 212(1) pm).