PHOTOCHEMICAL-REACTION OF W(CO)(6) WITH SNCL4 .4. SYNTHESIS OF NEW TUNGSTEN ALKYNE COMPLEXES - X-RAY CRYSTAL-STRUCTURE OF U(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 (phen ylacetylene, tert-butylacetylene, 3-hexyne and diphenylacetylene at ro om 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 labil e in solution and lose CO ligands. After exposure of a mixture of [WCl 2(CO)(2)(eta(2)-PhC=CPh)(2)] and [WCl(SnCl3)(CO)(eta(2)-PhC=CPh)(2)] t o moist air the complex u(3)-O)(mu-OH)(2)(mu-Cl)(2)(O)(eta(2)-PhC=CPh) (5)] (6) was isolated and its structure determined by X-ray crystallog raphy. 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 trinucle ar 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 compou nd to be isolated containing two different triply-bridged, mu(3)-O and mu(3)-Cl, ligands.