Reactivity of the Substituted Butadienes, Isoprene and Myrcene, with Decamethylsamarocene

The interaction of the substituted diene monomers isoprene, C₅H₈, and myrcene, C₁₀H₁₆, with a lanthanide was probed by examining their chemistry with (C₅Me₅)₂Sm. CH₂CHC(Me)CH₂reacts with (C₅Me₅)₂Sm to form the bimetallic [(C₅Me₅)₂Sm]₂[μ-η²:η⁴-CH₂CHC(Me)CH₂], 1. Both (C₅Me₅)₂Sm components in 1 exhibit trivalent metrical parameters. One Sm is oriented toward all four of the dienyl carbon atoms at distances of 2.604(9)−2.799(8) Å, and the other Sm interacts with only two carbons at distances of 2.544(9) and 2.674(9) Å. CH₂CHC(CH₂)CH₂CH₂CHCMe₂ reacts with (C₅Me₅)₂Sm to form [(C₅Me₅)₂Sm]₂[μ-η²:η⁴-CH₂CHC(CH₂)CH₂CH₂CHCMe₂], 2, which is similar in structure to 1. The double bond of the pendant olefinic substituent attached to the diene in myrcene does not coordinate. The structures of 1 and 2 are compared to the (C₅Me₅)₂Sm/PhC⋮CPh bimetallic reaction product [(C₅Me₅)₂Sm]₂[μ-η¹:η¹-PhCCPh], 3, which also contains two (C₅Me₅)₂Sm units attached to an unsaturated hydrocarbon, but has equivalent trivalent (C₅Me₅)₂Sm units. Each Sm in 3 interacts with the reduced (PhC⋮CPh)^2- primarily through a 2.52−2.54 Å Sm−C bond, although an ortho phenyl carbon is oriented toward each metal at a distance of >2.96 Å.