Photochemical reaction of W(CO)(6) with SnCl4 .4. Synthesis of new tungsten alkyne complexes: X-ray crystal structure of [W-3(mu(3)-O)(mu-OH)(2)(mu-Cl)(2)(O)(eta(2)-PhC CPh)(5)]

Reaction of [(CO)(4)W(mu-Cl)(3)W(SnCl3)(CO)(3)] (1) with alkynes (phenylacetylene, tert-butylacetylene, 3-hexyne and diphenylacetylene at room temperature initially affords the mixture of products [WCl2(CO)(2)(eta(2)-alkyne)(2)] (2-5) and [WCl(SnCl3)(CO)(eta(2)-alkyne)(2)] (2'-5') in quantitative yields. Tungsten(II) alkyne complexes are very labile in solution and lose CO ligands. After exposure of a mixture of [WCl2(CO)(2)(eta(2)-PhC=CPh)(2)] and [WCl(SnCl3)(CO)(eta(2)-PhC=CPh)(2)] to moist air the complex [W-3(mu(3)-O)(mu-OH)(2)(mu-Cl)(2)(O)(eta(2)-PhC=CPh)(5)] (6) was isolated and its structure determined by X-ray crystallography. The molecule consists approximately of an isosceles triangle of W atoms joined by triply-bridging oxygen. The longer edge is bridged by two chlorine atoms. The shorter edges are bridged by hydroxy groups. Compound 6 is noteworthy since it is among the first of the trinuclear complexes in which a mixed-valence (W2WIV)-W-II-(mu(3)-O) core has been established. It is also unique in being the first tungsten compound to be isolated containing two different triply-bridged, mu(3)-O and mu(3)-Cl, ligands.