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. CH2CHC(Me)CH2 reacts 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.
CH2CHC(CH2)CH2CH2CHCMe2 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.