Formation of [feM(η-C<inf>5</inf>H<inf>5</inf>)(CO) <inf>4</inf>(μ-CO)(μ-CR≡CR′H)] (M = Fe or Ru) complexes from the reaction of [mH(η-C<inf>5</inf>H<inf>5</inf>)(CO)<inf>2</inf>] with [fe<inf>2</inf>(CO)<inf>9</inf>] and acetylenes. X-Ray structure of [feRu(η-C<inf>5</inf>H<inf>5</inf>)(CO) <inf>4</inf>(μ-CO)(μ-CPh≡CPhH)]

The complexes [MH(η-C5H5)(CO)2] (M = Fe or Ru) react with an equimolar [Fe2(CO)9]-acetylene mixture in tetrahydrofuran affording [FeM(η-C5H5)(CO) 4(μ-CO)(μ-CR=CR′H)][M = Fe, R = R′ = Ph, (1), or H, (2); R = Ph, R′ = H (3); R = H, R′ = But, (4); M = Ru, R = R′ = Ph (5); R = SiMe3, R′ = H (6)]. The structure of (5) was established by single-crystal X-ray crystallography. It crystallizes in the space group P21/n with Z = 4 and a = 14.863(4), b = 14.542(4), c = 10.186(3) Å, and β = 97.09(3)°. The structure was solved by direct methods and refined by least squares to a final R of 0.067. It consists of Ru(C5H5)(CO) and Fe(CO)3 fragments linked by CO and 1,2-diphenylethenyl bridges and a metal-metal bond. A possible mechanism for the formation of the complexes is proposed on the basis of the activation of the acetylenes by [Fe2(CO)9] and subsequent insertion into the M-H (M = Fe or Ru) bond.