SYNTHESIS AND CYCLIZATION REACTIONS OF ALKYNYL(ETA-5-CYCLOPENTADIENYLTRICARBONYLMOLYBDENUM AND -TUNGSTEN) COMPLEXES

Cyclization of the organometallic complexes CH3C≡C(CH2)nM(C5H5)(CO)3(n = 3, 4, 5; I, M = Mo; II, M = W) occurred under mild conditions to give cyclized products M(CH5)(CO)2[C(CH3)═C(O){CH2)n] (III, M = Mo; IV, M = W) derived from intramolecular insertion of the acetylcnic function into a metal-acyl bond. Yields of III were high (>70%) for n = 3, moderate (~50%) for n = 4, and lower (<15%) for n = 5. No other isomers or products of insertion into metal-alkyl bonds were observed. Cleavage of the organic ligand from III (n = 4) under CO with CF3COOH gave 2-ethylidenecyclohexanone and CF3CO2Mo(C5H5)(CO)3in >90% yield. Hydrogenation of III (n = 4) gave 2-ethylcyclohexanone and [Mo(CsH5)-(CO)2]2in > 90% yield. Protonation of CH3C≡C(CH2)4W(C5H5)(CO)3gave the bis acetylene complex, W(CH5)(CO)2(2-heptyne)2+. © 1979, American Chemical Society. All rights reserved.