Hydride Mobility in Trinuclear Sulfido Clusters with the Core [Rh₃(μ‐H)(μ₃‐S)₂]: Molecular Models for Hydrogen Migration on Metal Sulfide Hydrotreating Catalysts

Abstract

Reaction of [Rh(µ-SH)

Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy

“…The mechanism of this exchange involves direct transfer of the β‐agostic hydrogen atom from the ethyl group to the ethylene ligand. An observation of slow (Δ G ≠ =17–18 kcal mol −1 ) hydride mobility was made by Oro and colleagues in Ir 3 S 2 cluster complexes …”

“…[247] The mechanism of this exchange involves direct transfer of the b-agostic hydrogen atom from the ethyl group to the ethylene ligand.A n observation of slow (DG ¼ 6 = 17-18 kcal mol À1 )h ydride mobility was made by Oro and colleagues in Ir 3 S 2 clusterc omplexes. [248] Interaction of acids with boron-rich cage [B 10 H 10 ] 2À 167 was examined by exchange NMR spectroscopy (Scheme 52). [249] The B 10 core of [B 10 H 11 ] À in 167 is similar in shape to that of [B 10 H 10 ] 2À where the eleventhHatom asymmetrically caps a polar face of the cluster.V ariable-temperature multinuclear NMR studies shed light on the dynamic nature of 167-H in solution:incontrast to 167,the boron cage is fluxional at moderate temperatures.…”

Polyhedral Flexibility in the Sulfido-Capped Cluster H2Ru3(CO)9(μ3-S) on Reaction with 2-(Diphenylphosphino)thioanisole (PS) and Reversible Tripodal Rotation of the Chelated PS Ligand in H2Ru3(CO)7(κ2-PS)(μ3-S)

“…Ligand-induced scission of unsupported metal–metal bonds and metal-capping ligand bonds is known, but the conversion of a hydride-bridged Ru–Ru bond to a terminal hydride group in a metal cluster following ligand addition is unprecedented. Hydride mobility in metal clusters is well-documented, and fluxionality involving hydride transit across intact metal–metal bonds via bridge-terminal-bridge exchange sequences, while common, does not result in the formation of a terminal metal-hydride (M–H) at the expense of the original metal–metal bond.…”

Bis(hydrosulfido)-bridged dinuclear rhodium(i) complexes as a platform for the synthesis of trinuclear sulfido aggregates with the core [MRh2(μ3-S2)] (M = Rh, Ir, Pd, Pt, Ru)

“…However, the dinuclear complexes [Rh(μ-SH)L 2 ] 2 also behave as precursors for the controlled synthesis of diverse homo-and heterotrinuclear hydrido-sulfido clusters with the core [MRh 2 (μ-H)(μ 3 -S) 2 ] (M = Rh, Ir). 15 Interestingly, some of these clusters exhibited a mobile hydride ligand that migrates between edge-bridging sites through the bridging sulfido ligands.…”

“…The 48-valence-electron clusters can be described as composed by two metal-metal bonded 16-electron M II metal atoms, with square-pyramidal geometries due 35 to the coordination to the bridging hydride ligand, and a 16-electron square-planar M I centre. 14,15 The formation of the core [MRh 2 (µ-H)(µ 3 -S) 2 ] is a consequence of the deprotonation of a hydrosulfido ligand in the presence of d 8 metal fragments to give the trinuclear hydrosulfido-sulfido intermediates with the core 40 [MRh 2 (µ 3 -SH)(µ 3 -S)] that collapse to the hydrido-sulfido clusters by a intramolecular proton transfer (pathway i, Scheme 1). Alternatively, the deprotonation of both hydrosulfido ligands should result in the formation of the anionic [Rh 2 (1).…”