Heating W(CO)(PhC=CPh)(3) (1) and diphenylacetylene in a sealed tube l
eads to alkyne-alkyne coupling to yield W(CO)(PhC=CPh)(2)(eta(4)-C4Ph4
) (2), W(CO)(PhC=CPh)(eta(5)-C3Ph3(C5Ph5)) (3), and W(CO)(PhC=CPh)(eta
(6)-C3Ph3(C5Ph5)) (4) together with the tungstenocene oligomer [W(C5Ph
5)(2)](x) (5). Oxidation of 5 by diiodine affords W(eta(5)-C5Ph5)(2)(I
)(2) (6), which is converted into the oxo complex W(eta(5)-C5Ph5)(2)(=
O) (7) by treating with AgBF4 in wet dichloromethane solution. Reactio
n of W(NCMe)(PhC=CPh)(3) (8) and 1 equiv of diphenylacetylene produces
W(NCMe)(PhC=CPh)(2)(eta(4)-C4Ph4) (9), whereas a similar reaction in
the presence of excess diphenylacetylene gives mainly the metallacycli
c complex W(PhC=CPh)(eta(8)-C8Ph8) (10). Compound 10 reacts with carbo
n monoxide to afford 3 and 4, while thermolysis of pure 10 results in
5 exclusively. The reaction mechanism has been explored by C-13 labeli
ng experiments. The structures of 7 and 10 have been established by an
X-ray diffraction study. The bonding of pentaphenylcyclopentadienyl l
igands of 7 is best described as a localized eta(3):eta(2) fashion. Co
mpound 10 contains a tungstenacyclononapentaene ring with two tungsten
-carbon double bonds.