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|Type:||Artigo de periódico|
|Title:||Synthesis and characterisation of saturated and unsaturated triruthenium clusters containing electronically symmetrical and asymmetrical alkynes|
|Abstract:||The synthesis and characterisation Of mu(3)-eta(2)-alkynyl triruthenium clusters, [Ru-3(mu(3)-eta(2)-R-1-4-C6H4CCR2)(mu-dppm)(mu-CO)(CO)(7)] (1, saturated), [Ru-3(mu-eta(2)-R-1-4-C6H4CCR2)(mu-dppm)(CO)(7)] (2, unsaturated) and [Ru-3(mu(3)-eta(2)-R-1-4-C6H4CCR2)(mu-dppm)(PPh3) (CO)(7)] (3, saturated) containing symmetrical and asymmetrical alkynes in which R-1 and R-2 are electron donor or electron withdrawing groups in the para position of the aromatic ring(s) or R 2 is ferrocenyl, are reported. Clusters I were obtained from the reactions of [PPN][Ru-3(mu-Cl)(CO)(10)] with R-1-4-C6H4CCR2 and dppm. Clusters I were successfully decarbonylated to give unsturated clusters 2, with the exception of the FcCCC(6)H(4)-4-NO2 containing cluster, which is stable. Novel adducts 3 were obtained in high yields by addition of PPh3 to unsaturated clusters 2. Clusters 1-3 were characterised by analytical and spectroscopic data, and structures were proposed on the basis of systematic P-31 NMR studies and correlations with X-ray structural data of related compounds available in the literature. Saturated compounds 1 contain a CO and a dppm ligands bridging the same edge, which is also parallel to the mu(3)-eta(2)-alkyne, as opposed to the structure previously proposed for the PhCCPh and other derivatives, and established by X-ray crystallography for the PhCequivalent toCCCPh cluster derivative, in which the dppm ligand bridges a different edge. Unsaturated compounds 2 exhibit the same structure established for the PhCCPh derivative in the solid state, with the alkyne bonded in the mu(3)-eta(2)-mode perpendicular to the Ru-2 edge supported by the dppm ligand. Because the dppm phosphorus chemical shifts were sensitive to the alkyne electronic asymmetry, it was possible to show that clusters containing electronically asymmetrical alkynes exist in two inseparable isomeric forms, which differ with respect to the alkyne orientation. Similarly to their osmium analogues, saturated compounds 3 exist as inseparable mixtures of isomers that differ with respect to the position of the bridging CO and dppm ligands, and in the cases of asymmetrical alkyne derivatives, also with respect to the orientation of the alkyne. This work has established, therefore, that mu-CO and dppm ligand positions respective to the mu(3)-eta(2)-alkyne in saturated clusters 1 and 3 are sensitive both to the nature of the coordinated alkyne and to the presence of a PPh3 in place of a CO ligand on the metal frame. (C) 2003 Elsevier B.V. All rights reserved.|
|Editor:||Elsevier Science Sa|
|Appears in Collections:||Artigos e Materiais de Revistas Científicas - Unicamp|
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