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Reactions of μ 3 ‐Alkenyl Triruthenium Carbonyl Clusters with Alkynes: Synthesis of Trinuclear μ‐//‐Alkyne, μ‐Vinylidene, and μ‐Dienoyl Derivatives
Author(s) -
Cabeza Javier A.,
del Río Ignacio,
MartínezMéndez Lorena,
PérezCarreño Enrique
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200600465
Subject(s) - diphenylacetylene , alkyne , chemistry , phenylacetylene , ligand (biochemistry) , acetylene , medicinal chemistry , stereochemistry , toluene , propyne , cluster (spacecraft) , catalysis , photochemistry , organic chemistry , biochemistry , receptor , computer science , programming language
The reactions of doubly face‐capped triruthenium cluster complexes of the type [Ru 3 (μ 3 ‐ κ 2 ‐HNNMe 2 )(μ 3 ‐ κ 2 ‐R 2 CCHR 1 )(μ‐CO) 2 (CO) 6 ] (HNNMe 2 = 1,1‐dimethylhydrazide; R 2 CCHR 1 = alkenyl ligand) with terminal and internal alkynes have been studied in refluxing toluene. The following derivatives have been isolated from these reactions: [Ru 3 (μ 3 ‐ κ 2 ‐HNNMe 2 )(μ 3 ‐ κ 2 ‐R 2 CCHR 1 )(μ‐ κ 2 ‐//‐HCCH)(CO) 7 ] (R 1 = R 2 = H, 5 ; R 1 = Ph, R 2 = H, 6 ; R 1 = CH 2 OMe, R 2 = H, 7 a ; R 1 = H, R 2 = CH 2 OMe, 7 b ) from acetylene, [Ru 3 (μ 3 ‐ κ 2 ‐HNNMe 2 )(μ 3 ‐ κ 2 ‐HCCH 2 )(μ‐ κ 2 ‐//‐PhCCPh)(CO) 7 ] ( 11 ) from diphenylacetylene, and three isomers of [Ru 3 (μ 3 ‐ κ 2 ‐HNNMe 2 )(μ 3 ‐ κ 2 ‐HCCH 2 )(μ‐ κ 2 ‐//‐PhCCH)(CO) 7 ] ( 14 , 15 a , and 15 b ) from phenylacetylene. These products result from substitution of a CO ligand by the alkyne and contain an RuRu edge bridged by the alkyne ligand in a parallel manner. DFT calculations on selected isomeric products have helped to establish that the type of RuRu edge bridged by the alkyne depends more on kinetic factors related to the size of the alkyne substituents than on the thermodynamic stability of the final products. The preparation of triruthenium cluster complexes with μ‐//‐alkyne ligands is unprecedented and seems to relate to the fact that the starting trinuclear complexes have their two triangular faces protected by capping ligands. The clusters bearing μ‐//‐acetylene ( 5 – 7 ) are thermodynamically unstable with respect to their transformation into edge‐bridging vinylidene derivatives, [Ru 3 (μ 3 ‐ κ 2 ‐HNNMe 2 )(μ 3 ‐ κ 2 ‐HCCHR)(μ‐ κ 1 ‐CCH 2 )(CO) 7 ] (R = H, 8 ; Ph, 9 ; CH 2 OMe, 10 ). DFT calculations have shown that complex 8 is 11.2 kcal mol −1 more stable than its precursor 5 . The thermolysis of compound 11 leads to [Ru 3 (μ 3 ‐ κ 2 ‐HNNMe 2 )(μ‐ κ 4 ‐H 2 CCHCPhCPhCO)(μ‐CO) 2 (CO) 5 ] ( 12 ), which contains a novel edge‐bridging dienoyl ligand that arises from an unusual coupling of diphenylacetylene, carbon monoxide, and the ethenyl ligand of complex 11 . A chloro‐bridged dimer of trinuclear clusters, [Ru 6 (μ‐Cl) 2 (μ 3 ‐ κ 2 ‐HNNMe 2 ) 2 (μ 3 ‐ κ 2 ‐HCCH 2 ) 2 (μ‐ κ 2 ‐PhCCHPh) 2 (μ‐CO) 2 (CO) 10 ] ( 13 ), has been prepared by treating compound 11 with hydrogen chloride. Therefore, edge‐bridging parallel alkynes are susceptible to protonation to give edge‐bridging alkenyl ligands. Compound 13 is the first complex to contain two alkenyl ligands on a trinuclear cluster, one face‐capping and the other edge‐bridging.