Trinuclear ruthenium pentahydride complex (Cp 'Ru)
3 (μ-H)
3 (μ
3-H)
2 (1 : Cp ' = η-C
5Me
5) reacts with a series of acyclic conjugated dienes such as butadiene, isoprene, or penta-1, 3-diene to form trinuclear μ
3-1, 3-dimetalloallyl complexes 2 by way of an intermediary μ
3-η
2 : η
2-s-cis-1, 3-diene complex. In the reactions with butadiene and isoprene, an agostic intermediate, in which three ruthenium centers concertedly activate a 1, 3-diene by taking the role of coordination sites and an activation site, is detected by
1H and
13C NMR. The intermediary 1, 3-diene complexes with agostic interaction undergo C (sp
2) -H bond cleavage at room temperature to generate 1, 3-dimetalloallyl complexes. The reaction of 1 with cyclopentadiene generates a trinuclear p
3-2-methylruthenacyclopentadiene complex 4 as a result of cleavage of the unactivated C (sp
3) -C (sp
2) bond. In the reaction of 1 with 1, 3-cyclohexadiene, cleavage of an allylic C-H bond followed by the β-H elimination affords α μ
3-η
2 : η
2 : η
2-benzene complex.
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