Reactivity Studies of Para-Hydrogen with μ₃-Quinolyl Triosmium Clusters

Abstract

The reactions of the cluster complexes Os 3 -(CO) 9 (µ 3 -η 3 4), and Os 3 (CO) 9 (µ 3 - 5) with para-hydrogen have been studied at ∼3 atm and 90-110 °C. In all cases, reaction at the metal core is the initial product and polarization enhanced polyhydride intermediates are observed. The chemical shifts and relative intensities of these resonances are used to extract mechanistic information about the reactivity of 1-5. As with previous studies on related electron-deficient complexes, 3-5 show reactivity that is very sensitive to the substituent in the 5-position.

Parahydrogen-based NMR methods as a mechanistic probe in inorganic chemistry

“…These investigations, conducted on the tri-ruthenium clusters Ru 3 (CO) 10 (PMe 2 Ph) 2 and Ru(CO) 10 (PPh 3 ) 2 , used EXSY experiments to monitor the interconversion of the three isomers of each cluster; the activation parameters of these processes were measured, and their solvent dependency was also investigated. Similar processes in a series of 3 -quinolyl tri-osmium clusters were studied by Aime and co-workers [53].…”

Catalytic Hydrogenation by Triruthenium Clusters: A Mechanistic Study with Parahydrogen‐Induced Polarization

“…[27] PHIP has recently been used to study triosmium m 3quinolyl trihydride clusters, whereby the observation of enhancement for all three hydride resonances has been attributed to the existence of fluxionality and cross-polarisation effects. [28] In these clusters, use of p-H 2 has led to the association of OsÀOs bond breakage with the hydrogen addition step. Indirect evidence was also presented that H 2 can be transferred onto the quinolyl moiety, leading to its dissociation.…”

Asymmetric hydrogenation of an α-unsaturated carboxylic acid catalyzed by intact chiral transition metal carbonyl clusters – diastereomeric control of enantioselectivity

“…both S,S-1b and R,R-1b were identified in the structure even though enantiopure S,S-1b had been used in the synthesis of cluster 5. Our explanation for this surprising result is that a small amount of R,R-1b was present in the ligand batch used, and the resultant isomer of 5 co-crystallized with the (majority) product (12), Ru1-P2 2.341(2), Ru2-P1 2.361(2), Ru1-S1 2.359(2), Ru2-S1 2.357(2), Ru3-S1 2.355(3), Ru1-H1 1.72(5), Ru1-H2 1.678 (17), Ru2-H2 1.57(5), Ru3-H1 1.57 (4). Thermal ellipsoids are drawn at the 50% probability level and C-H hydrogen atoms have been omitted for the sake of clarity.…”

“…15 Parahydrogen (p-H 2 ) NMR methods have been used to identify active catalysts in hydrogenation reactions. 16,17 By using such techniques, Blazina and co-workers have demonstrated that the clusters [H 2 Ru 3 (CO) 10 (L) 2 ] (L = PMe 2 Ph or PPh 3 ) function as homogeneous catalysts for the hydrogenation of alkynes (diphenylacetylene). 18 The active catalysts that were identified are derived from the dihydride species [HRu 3 (µ-H)(CO) 9 (L) 2 ].…”