SYNTHESIS AND CRYSTAL-STRUCTURES OF THE TUNGSTEN(VI)-ALKYNE COMPLEXES [W-2(O)(OME)(6)(ET-SE-C-C-SE-ET)(2)] AND LI[W(OME)(5)(ET-TE-C-C-TE-ET)]

The title compounds have been prepared by reactions of lithium methanolate with [WCl4(Et-Se-C=C-Se-Et)(THF)] and [WCl4(Et-Te-C=C-Te-Et)(THF)], respectively, in diethylether suspensions. Both complexes were characterized by crystal structure determinations. [W-2(O)(OMe)(6)(Et-Se-C=C-Se-Et)(2)]: Space group P1 $($) over bar$$, Z = 2, structure determination with 4320 observed unique reflections, R = 0.041. Lattice dimensions at -70 degrees C: a = 949.3, b = 1225.3, c = 1285.0 pm, alpha = 82.48 degrees; beta = 82.44 degrees; gamma = 81.44 degrees. The tungsten atoms are bridged by three mu(2)-O-atoms of the OMe groups; the alkyne ligands are coordinated side-on in a metallacyclopropene-like fashion. Li[W(OMe)(5)(Et-Te-C=C-Te-Et)]: Space group P1 $($) over bar$$, Z = 2, structure determination with 9381 observed unique reflections, R = 0.038. Lattice dimensions at -70 degrees C: a = 983.4, b = 1606.9, c = 1971.5 pm, alpha = 66.09 degrees, beta = 84.29 degrees, gamma = 79.83 degrees. The lithium ions link the [W(OMe)(5)(Et-Te-C=C-Te-Et)](-) anions to a trimeric ion ensemble via the O atoms of three OMe groups of each anion.