Selective Synthesis of a Triruthenium Pentahydrido Complex with Mixed-Cp Ligands (C₅^tBu₃H₂ and C₅Me₅) and Its Transformation into Face-Capping Benzene Complexes: Fluxionality of a Face-Capping Benzene Ligand Induced by Oxidation

Abstract

A mixed-ligand triruthenium μ-chloro complex, [(Cp‡Ru)­(Cp*Ru)2(μ-H)4(μ-Cl)] (7; Cp‡ = η5-C5 t Bu3H2, Cp* = η5-C5Me5) was synthesized by the reaction of [{Cp*Ru­(μ-H)2}2] (5a) with [{Cp‡Ru­(μ-Cl)}2] (6). The subsequent treatment of 7 with 2-propanol and a base resulted in the replacement of the μ-Cl ligand by a hydride and afforded a mixed-ligand triruthenium pentahydrido complex, [(Cp‡Ru)­(Cp*Ru)2(μ-H)3(μ3-H)2] (1b), which is the analogue of the D 3h symmetrical [{Cp*Ru­(μ-H)}3(μ3-H)2] (1a). The pseudo C s symmetrical Ru3 skeletons of 1b and 7 supported by one Cp‡ and two Cp* were unambiguously confirmed by X-ray diffraction. The Ru3 skeleton of 1b promoted the evaluation of the mobility of a face-capping benzene ligand in [(Cp‡Ru)­(Cp*Ru)2(μ-H)3(μ3-η2:η2:η2-C6H6)] (2b), which was prepared by the reaction of 1b with 1,3-cyclohexadiene or benzene. Unlike previously reported face-capping benzene complexes, in which the μ3-η2:η2:η2-C6H6 ligand rotates rapidly on the trinuclear plane, the variable-temperature NMR study showed that the face-capping benzene in 2b does not rotate on the Ru3 plane even at 80 °C. This was likely due to the electron-rich nature of the Ru3 site, which strongly binds the benzene ligand. In contrast, the μ3-η3:η3-C6H6 ligand in [(Cp‡Ru)­(Cp*Ru)2(μ-H)3(μ3-η3:η3-C6H6)]2+ (4b), obtained by the two-electron oxidation of 2b, rotated rapidly due to the reduced back-donation from the dicationic Ru3 site.

Syntheses and Properties of Triruthenium Polyhydrido Complexes Composed of 1,2,4-tri-tert-butylcyclopentadienyl and p-Cymene Ruthenium Units

“…The formation of 2a in the reaction indicated the competitive degradation of the dinuclear skeleton of 1b, which was in contrast to the selective formation of [(Cp*Ru) 2 (Cp ‡ Ru)(μ-H) 3 (μ 3 -H) 2 ] (4) in the reaction of 1a with [Cp ‡ RuCl] 2 . 36 This is probably because of the sterically demanding diruthenium site of 1b, which suppresses The metrical parameters of 3a are nearly identical with those of the benzene analogue 3b, 35 and the Ru−Ru distances (2.7430(5), 2.7260(5), and 2.7104(5) Å) are comparable to those of [{Cp*Ru(μ-H)} 3 (μ 3 -H) 2 ] (6) (2.7453(6)−2.7544(8) Å). 21 Although the Ru−Ru distances correspond to a Ru−Ru single bond, no bond critical points and bond paths were found at any of the Ru−Ru edges in both 3a and 6 by a QTAIM analysis (Figure S7 in the Supporting Information).…”

“…For the reaction conducted at 80 °C for 16 h, 2a and 3a were obtained in 26% and 17% yields, respectively. The formation of 2a in the reaction indicated the competitive degradation of the dinuclear skeleton of 1b , which was in contrast to the selective formation of [(Cp*Ru) 2 (Cp ‡ Ru)­(μ-H) 3 (μ 3 -H) 2 ] ( 4 ) in the reaction of 1a with [Cp ‡ RuCl] 2 . This is probably because of the sterically demanding diruthenium site of 1b , which suppresses the efficient incorporation of a [( p -cymene)­Ru] fragment.…”

“…We also reported that a diruthenium tetrahydrido complex, [(Cp*Ru) 2 (μ-H) 4 ] (1a), reacts with [Cp ‡ RuCl] 2 in the presence of 2-propanol and a base to yield a mixed-ligand trinuclear complex, [(Cp*Ru) 2 (Cp ‡ Ru)(μ-H) 3 (μ 3 -H) 2 ] (4) (Scheme 1b). 36 This implied that a mixed-ligand trinuclear skeleton could be constructed by the reaction of a coordinatively unsaturated dinuclear hydrido complex with a metal halide. This, in turn, prompted us to prepare mixedligand triruthenium hydrido complexes composed of [Cp ‡ Ru] and the more soluble [(p-cymene)Ru] fragments.…”

Photo-Induced Reaction of Cp*Ru(μ-H)4RuCp* with Arenes Resulting in Irreversible Formation of μ-η2:η2-Cyclohexadiene Complexes

“…Investigation of the reaction modes of multinuclear polyhydrido complexes with arenes would provide profound insight into the interaction between metal surfaces and arene molecules as metal clusters have been considered to be a simplified structural model of metal surfaces. − We have reported the reactions of di- and trinuclear polyhydride clusters, [Cp*Ru­(μ-H) 4 RuCp*] ( 1 ) and [{Cp*Ru­(μ-H)} 3 (μ 3 -H) 2 ] ( 3 ), with benzene under thermally excited conditions. − Complex 1 reacts with benzene at 70 °C to produce a dinuclear cyclohexadiene complex, [{Cp*Ru­(μ-H)} 2 (μ-η 2 :η 2 -C 6 H 8 )] ( 2 ), accompanied by dinuclear skeleton fragmentation. A triruthenium pentahydrido complex 3 and tetraruthenium hexahydrido complex, [(Cp*Ru) 4 (μ-H) 2 (μ 3 -H) 4 ] ( 4 ), were also produced during the reaction.…”

Quantum Theory of Atom in Molecules Investigation Trinuclear Ruthenium: DFT Approach

“…The electrical structures of low valent transition metal clusters receive a lot of attention 3,4 due to their importance as catalysts in industries and the atypical nature of metal-metal bonds, which are still unexplained to several extent 5,6 . A variety of experimental charge density experiments on M-M bonded compounds have been conducted in response to this interest 7,8 .…”