Synthesis and Structural Investigation of a New Bimetallic Alkoxide with the Composition Mg2Sb4(OC2H5)16

Abstract

The new bimetallic antimony alkoxide Mg2Sb4(μ3-OEt)2(μ-OEt)8(OEt)6 has been prepared by reacting Mg(OEt)2 with an excess of Sb(OE1)3 in a toluene-ethanol solution, and its molecular structure has been established by single crystal X-ray diffraction techniques. The compound crystallizes with the triclinic space group symmetry P1̄ . The unit cell, which contains one formula unit, has the dimensions a = 9.128(4), b = 12.168(4), c = 12.640(6) Å, α = 64.06(2)°, β = 79.96(2)°, and γ = 87.29(2)°. The derived structural model has been refined against the 3235 most significant observed X-ray reflections, collected at 170(2) K, to an R-value of 0.030. The molecular structure has a major fragment similar to that found in tetrameric alkoxides or bimetallic alkoxides with the compositions M4(OR)m and M2M′2 (OR)n, respectively. The metal-oxygen skeleton of the fragment forms a rather rigid unit, as judged by an analysis of the determined thermal displacement parameters. The Mg2+ ions are octahedrally coordinated by the ethoxy oxygen atoms and the Sb3+ ions can be considered to have a trigonal bipyramidal coordination when the four ethoxy oxygen atoms and the lone pair are taken into account. Extended Hückel calculations verify that the Mg-O bonds are rather ionic, while the shorter Sb-O bond are more covalent.