| Reaction of N-phenyl-2,5-dimethyl-3,4-diphenylcyclopenta-2,4-dienimine (6) with Ru3(CO)12 formed two isomers of {lcub}[2,5-Me2-3,4-Ph2(η5-C4CNHPh)]Ru(CO)(μ-CO){rcub} 2 (8-trans and 8-cis). Photolysis of 8 under a H2 atmosphere led to the formation of the aminocyclopentadienyl ruthenium hydride [2,5-Me2-3,4-Ph2(η5-C 4CNHPh)]Ru(CO)2H (9-H). 9-H reduced benzaldehyde slowly at 75°C to give benzyl alcohol and 8. Protonation of 9-H with triflic acid produced {lcub}[2,5-Me2 -3,4-Ph2(η5-C4CNH2Ph)]Ru(CO) 2H{rcub}OTf (11-H), which reacted rapidly with benzaldehyde at −80°C. Upon warming to room temperature, benzyl alcohol and [2,5-Me 2-3,4-Ph2(η5-C4CNHPh)]Ru(CO) 2OTf (9-OTf) were identified as products. Reaction of 9-OTf with H2 and base led to the reformation of 9-H. These reactions provide the transformations required for a catalytic cycle for hydrogenation of aldehydes.; Reaction of [2,5-Me2-3,4-Ph2(η5-C 4CNHPh)]Ru(CO)2Cl with a silver salt (AgOTf, AgBF4, AgPF6) in the presence of benzyl alcohol led to the formation of {lcub}[2,5-Me2-3,4-Ph2(η5-C4CNHPh)]Ru(CO) 2(HOCH2Ph){rcub}+. With OTf as the anion, there was an equilibrium between ([2,5-Me2-3,4-Ph2(η 5-C4CNHPh)]Ru(CO)2(HOCH2Ph){rcub} + and [2,5-Me2-3,4-Ph2(η5-C 4CNHPh)]Ru(CO)2OTf (9-OTf) (Δ H° = −6.6 ± 0.5 kcal mol−1 and ΔS° = −19 ± 3 eu). {lcub}[2,5-Me 2-3,4-Ph2(η5-C4CNHPh)]Ru(CO) 2(η1-O=CMe2){rcub}+ (BF 4 and PF6) were synthesized from reaction of [2,5-Me 2-3,4-Ph2(η5-C4CNHPh)]Ru(CO) 2Cl with a silver salt and acetone. The equilibrium constant between {lcub}[2,5-Me2-3,4-Ph2(η5-C4CNHPh)]Ru(CO) 2(HOCH2Ph){rcub}+ and {lcub}[2,5-Me2-3,4-Ph 2(η5-C4CNHPh)]Ru(CO)2(η 1-O=CMe2){rcub}+ was dependent on the anion. The rate of alcohol exchange into {lcub}[2,5-Me2-3,4-Ph2(η 5-C4CNHPh)]Ru(CO)2(HOCH2Ph){rcub} + was independent of the free alcohol concentration (Δ H‡ = 16.6 ± 1.0 kcal mol−1 and ΔS‡ = 3.4 ± 3.0 eu). The rate of alcohol dissociation from {lcub}[2,5-Me2-3,4-Ph 2(η5-C4CNHPh)]Ru(CO)2(HOCH 2Ph){rcub}+ was slow at −80°C compared to the rate of reaction of {lcub}[2,5-Me2-3,4-Ph2(η5-C 4CNH2Ph)]Ru(CO)2H{rcub}+ with benzaldehyde. The product mixture from the reaction {lcub}[2,5-Me2-3,4-Ph2(η 5-C4CNH2Ph)]Ru(CO)2H{rcub... |
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