CH activations in aldehydes in reactions with Ru5(μ5-C)(CO)15

Abstract

The reaction of Ru5(μ5-C)(CO)15, 1 with benzaldehyde yielded two new pentaruthenium carbido cluster compounds: Ru5(μ5-C)(CO)14[η2-O=C(H)C6H4](μ-H), 2 and Ru5(μ5-C)(CO)14(μ-η2-O=CPh)(μ-H), 3 containing open Ru5C cluster complexes formed by the activation of two different C-H bonds of the benzaldehyde molecule. Compound 2 contains a chelating, ortho-metallated benzaldehyde ligand coordinated to an open Ru5C cluster that is coordinated by the aldehyde oxygen atom and one of the ortho-positioned carbon atoms of the phenyl ring that was formed by loss of a CO ligand and an oxidative addition of the ortho-C-H bond of the phenyl ring to the metal atom. Compound 3 is an isomer of 2 that contains an O=C-coordinated, η2-bridging benzoyl ligand across the open edge of the Ru5C cluster formed by C-H activation at the aldehyde formyl group. The reaction of 1 with trans-cinnamaldehyde yielded two complexes: Ru5(μ5-C)(CO)14[η2-O=C(H)CH=CPh](μ-H), 4 and Ru5(μ5-C)(CO)14[μ-η2-O=CC(H) = C(H)Ph](μ-H), 5. Compound 4 contains an open Ru5 cluster with a chelating cinnamoyl ligand formed by coordination of the aldehyde oxygen atom and the β–carbon atom of the alkene double bond formed by a C-H activation at the alkene atom. Compound 5 contains a η2-bridging, O=C coordinated cinnamoyl group formed by C-H activation at the aldehyde formyl group. The reactions of 1 with furfural and 5-hydroxymethylfurfural yielded similar complexes: Ru5(μ5-C)(CO)14(μ-η2-O=CC4OH3)(μ-H), 6 and Ru5(μ5-C)(CO)14[μ-η2-O=CC4OH2(CH2OH)](μ-H), 7, respectively with each one containing bridging, O=C coordinated acyl ligand formed by C-H activation at the aldehyde formyl group. All of the new compounds were characterized by single-crystal X-ray diffraction analyses.