Catalyst design. The activation of a trinuclear metal cluster complex by metal atom substitution

Article abstract of DOI:10.1021/om00093a030

The trinuclear cluster complex Mo₂Ru(CO)₇(C₅H₅) ₂(μ₃-S) (1) has been shown to produce the oligomerization of HC₂Ph. The reaction of 1 with HC₂Ph at 98°C has yielded the products Mo₂Ru(CO)₂(C₅H₅) ₂[μ₃-η ⁶-HCC(Ph)C(H)C(Ph)C(H)C(Ph)](μ₃-S) (2) in 15% yield and Mo₂Ru(CO)₂(C₅H₅) ₂[μ-η³-PhCC(H)-CPh][μ³-η ³-HCC(Ph)CH](μ₃-S) (3) in 11% yield. 2 and 3 were characterized by crystallographic methods. For 2: space group P2₁/c, a = 10.899 (2) A?, b = 23.563 (5) A?, c = 14.562 (3) A?, β = 91.97 (2)°, Z = 4. The structure was solved by direct methods and was refined (3060 reflections) to the final value of the residuals R = 0.045 and R_w = 0.045. Compound 2 consists of a sulfur-bridged Mo₂Ru cluster that contains 1,3,5-triphenyldimetallahexatrienyl ligand bridging one face of the cluster. The hexatrienyl ligand was formed by the head-to-tail coupling of three HC₂Ph molecules. For 3: space group C2/c, a = 35.86 (1) A?, b = 12.454 (6) A?, c = 14.622 (3) A?, β = 98.60 (2)°, Z = 8. The structure was solved by direct methods and was refined (1867 reflections) to the final values of the residuals R = 0.054 and R_w = 0.051. Compound 3 consists of a sulfur-bridged Mo₂Ru cluster that contains a triply bridging 2-phenyldimetallaallyl ligand and an edge-bridging 1,3-diphenyldimetallaallyl ligand. 3 was formed from 2 by the splitting of the hexatrienyl ligand into two three carbon groupings. Compound 3 was obtained from 2 in 57% yield by heating to 125 °C, but this also yielded MO₂Ru(CO)₂(C₅H₅) ₂[μ-η³-HCCPhCPh][μ₃-η ³-HCCPhCH](μ₃-S) (4), an isomer of 3 in 38% yield. 4 was characterized by crystallographic methods: space group P1, a = 13.545 (2) A?, b = 15.869 (3) A?, c = 9.746 (2) A?, α = 90.37 (2)°, β = 104.11 (1)°, γ = 82.22 (1)°, Z = 2. The structure was solved by the heavy-atom method and refined (2717 reflections) to the final values of the residuals R = 0.044 and R_w = 0.042. 4 differs from 3 only in the structure of the edge-bridging dimetallaallyl group that has phenyl substituents in the 1- and 2-positions whereas 3 has the phenyl substituents in the 1- and 3-positions. 4 was obtained directly from 3, 24% yield, by heating to 125°C for 3 h. The compound MO₂Ru(CO)₅(C₅H₅) ₂[μ-η⁴-PhCC(H)CC(H)Ph](μ₃-S) (5) was obtained (11% yield) from the reaction of 1 with HC₂Ph in the presence of Me₃NO. The structure of 5 was determined crystallographically: space group P1, a = 12.906 (3) A?, b = 13.916 (4) A?, c = 9.708 (4) A?, α = 91.54 (3)°, β = 100.82 (2)°, γ = 95.48 (2)°, Z = 2. The structure was solved by the heavy-atom method and was refined (2522 reflections) to the final values of the residuals R = 0.050 and R_w = 0.054. 5 consists of an open Mo₂Ru cluster bridged by a sulfido ligand and a Ph(H)CCC(H)CPh group that is π-bonded to one metal atom and σ-bonded a second metal atom. This ligand appears to have been formed by a head-to-head coupling of two HC₂Ph molecules and was accompanied by a hydrogen atom shift. 5 does not appear to be an intermediate in the formation of 2, 3, or 4. The reactivity of 1 is compared with that of Ru₃(CO)₉(μ₃-HC₂Ph)(μ ₃-S) and Mo₂(CO)₄(C₅H₅)₂.