Structural studies of organometallic compounds in solution. II. Magnesium bromide and iodide in diethyl ether and tetrahydrofuran; an extended X-ray absorption fine structure (EXAFS) and large angle X-ray scattering(LAXS) study

Article abstract of DOI:10.1016/0022-328X(91)80115-Z

The structures of the magnesium iodide complexes formed in concentrated diethyl ether and tetrahydrofuran solutions have been determined by the large angle X-ray scattering (LAXS) technique.Those of the more dilute solutions of magnesium bromide in diethyl ether and tetrahydrofuran solutions have been determined by the extended X-ray absorption fine structure (EXAFS) method.The investigation of the MgI2 diethyl ether solution was carried out at 44 deg C since this solution cystallizes at about 30 deg C.This solution is probably best considered a melt, the structure of which can be regarded as a close-packing of iodide ions with magnesium ions occupying some of the holes.The coordination around a specific magnesium ion depends on whether it occupies a tetrahedral or an octahedral hole.The average Mg-I bond distance is 2.75 Angstroem.Solvated MgI⁺ is the dominating complex in MgI2-tetrahydrofuran solution.Magnesium is probably six-coordinate in this complex, and the Mg-I bond distance is 2.52(5) Angstroem.The Mg-Br bond distance is 2.49 and 2.66 Angstroem in diethyl ether and tetrahydrofuran, respectively.